Shell dull cream white, with three broad varices which are produced and slightly hooked inward at the shoulder, continuous from whorl to whorl, and extend to the end of the anterior canal. The tubes are included in the posterior hooks of the varices. Surface weakly marked with growth lines between the varices, where there is a median convexity. There are about six postembryonic whorls. The aperture is narrowly oval, with a thin, continuous inner peristome which has five small teeth within the outer lip and a corresponding series of pits behind the peristome; such pits are seen also in front of each varix on the last whorl, and three of them follow each varix of the earlier whorls. Length 15 mm., diam. 9 mm.
This is the Pacific analogue of Typhis cancellatus Sby. of the West Indies. The frills are much flatter in the present species. Simple but elegant in form, it is one of the most exquisite species of the genus.

The shell is small to moderately large (maximum length 18 mm) and broadly trigonal. The spire is high and acute, consisting of one and one-fourth nuclear whorls and six convex postnuclear whorls. The suture is obscured. The bodv whorl is large and broadly trigonal. The aperture is of moderate size and ovate, and forms an almost entirely erect peristome, the parietal margin being adherent. Each anal siphonal tube is coalescent with a broad shouldermargin spine of triangular cross section; although the tube originates within the varical plane, the dorsal side of the varical spine originates immediately after the preceding varix, afterwards sweeping ventrally and sharply posteriorly, to end with the distal end of the tube. The siphonal canal is broad and sealed, except for a short, barely open portion near its dorsally recurved anterior end. The body whorl bears three broadly alate varices. A series of two or three obliquely aligned nodules extends in each interspace from above the shoulder margin, in the direction of growth, to below the shoulder margin, just before the next varix. In addition, the shell bears 13 weak spiral cords, the seven on the canal barely discernible, the six on the body slightly heavier; the 13 cords are more apparent as serrations on the varical margin and on the interior of the outer apertural lip. Shell color is white, overlaid by a flat-white, minutely frilled intritacalx. The interior of the aperture is white to cream-colored.
A larger (to 23 mm), more coarsely sculptured form is known only from the Galapagos Islands.

Shell length primarily 14.0 mm and under (Wiedrick, 2012), extremely large specimens up to 19.2 mm, width 11.5mm (coll. RH), medium sized for the genus, shape ovate, spire tall, indented near suture of previous whorl, functional tubes long, pits shallow, weak or even absent, well-spaced, final varices thin, expanded, cords rounded at intersection. Intritacalx longitudinally lirate, squamous, shell color chalky white. Final whorl with (IP), P1, s1, (t), P2, P3, P4, P5, (s5), P6, ADP, MP, (ABP). Aperture elongate-ovate to ovate, columellar wall thick, projecting throughout, except near parietal wall. Apertural denticles D1-D5; denticles Dl broad, D2 and D3 occasionally both split, D4 and D5 small, low. Siphonal canal broad, short, 23-24% of total shell length, ventrally sealed, dorsally bent at tip.

Type locality. Mariato, Bahia Montijo, Veraguas Province, Panama, under rocks at low tide.
Other material examined. 35 lots from SBNHM; 18 lots from LACM; four specimens (RH).
Distribution. 4.8 km north of Puertecitos, Baja California, Mexico south; Punta San Antonio, Sonora, Mexico south to Isla de Malpelo, Colombia (Kaiser & Bryce, 2001), intertidal to 12.1 m (Wiedrick, 2012: 92) (Fig. 4).

Description. Shell length primarily 14.0 mm and under (Wiedrick, 2012), extremely large specimens up to 19.2 mm, width 11.5mm (coll. RH), medium sized for the genus, shape ovate, spire tall, indented near suture of previous whorl, functional tubes long, pits shallow, weak or even absent, well-spaced, final varices thin, expanded, cords rounded at intersection. Intritacalx longitudinally lirate, squamous, shell color chalky white. Final whorl with (IP), P1, s1, (t), P2, P3, P4, P5, (s5), P6, ADP, MP, (ABP). Aperture elongate-ovate to ovate, columellar wall thick, projecting throughout, except near parietal wall. Apertural denticles D1-D5; denticles Dl broad, D2 and D3 occasionally both split, D4 and D5 small, low. Siphonal canal broad, short, 23-24% of total shell length, ventrally sealed, dorsally bent at tip.

Discussion. The original, untypified description of Tripterotyphis lowei from Panama was noted as being 14.5 mm in length, 8.0 mm in width, a typical size for this mainland species. The specimen in ANSP, was noted as, "Type 155330 ANSP.; paratypes in Lowe collection" in Pilsbry & Lowe (1932: 77). Pilsbry (1931) never designated a holotype, therefore, the ANSP specimen is here considered a lectotype designated by Pilsbry & Lowe (1932) following ICZN article 74.5.
A recent specimen figured by Garrigues (2020: fig. 8a-b), labeled as a holotype is not the "holotype" nor the lectotype, and is of unknown origin. The ANSP type number referenced by the author, "(ANSP 84: 77)" appears to reference the ANSP Proceedings publication and pagination numbers (Pilsbry & Lowe, 1932: 77-78), not an actual lectotype number. Additionally, a protoconch figure (Ibid.: fig. 9b) was omitted in the caption and is also of unknown origin. The maximum depth of 250 m provided by Garrigues (2020: 41) is inconsistent with specimens analyzed in this study and no specific specimen data was cited and therefore needs confirmation. An examination of records in the LACM collection reveal a maximum depth of 12.1 m for this species. D'Attilio (1976) inadvertently reversed captions for the figured specimens illustrated on the lower left specimens, the left specimen morphologically matches T lowei and is here recognized as such. The Islas Cocos, Costa Rica and Isla de Malpelo, Colombia are closer in proximity and distance from the mainland, compared to the extreme distance of Islas Galapagos, Ecuador. Therefore, Islas Cocos specimens previously listed (Shasky, 1989: 74; Kaiser, 2001: 5) are a likely match to the Isla de Malpelo specimen figured by Kaiser & Bryce (2001: pl. 36, fig. 4) and are included above in the chresonymy for this species. The specimen figured as T arcana by Robin (2008: 281, fig. 6) appears to be a juvenile specimen that matches T lowei. Compared to the most similar species, T. galapagosensis, this species are lighter in weight, has an s5 cord, is absent of an ABP cord, is smaller in size and has a much less dramatic and sometimes absent IP cord.

Escondido Bay, Baja California, to Panama and the Galapagos Islands.