Biplex perca: -350m, Trawled from sand/gravel/mud bottom, East China Sea, Zhejiang, China, 83.5mm., 2014.
The « Maple Leaf Triton » is a most eccentric ranellid widely distributed across the Western Pacific region, from Japan to northern Australia and across the central Western Pacific islands. It is replaced by its sister species Biplex bozzettii Beu, 1998 with a consistently wider shell from southern India and westward into the Indian Ocean. A comm.on carnivorous species, it is mostly found on sandy to gravely bottoms around -50~200m deep although occasionally deeper. The shell is much compressed in the dorsal-ventral direction and has regular wing-like varices every 180 degrees, resulting in a flat and wide leaf-like shell; aptly described as « maple leaf » in the English vernacular name. The varices are fragile and prone to damage, it is difficult to find a large specimen with intact varices. The intervarical space carry beaded sculpture but the beading is normally not consistent throughout, unlike B. bozzettii. Typical shell length around 65mm. but it is very variable in size and giant specimens may reach even 100mm.

Biplex perca: Biplex perca is the largest of Biplex species; an unlocalised specimen in NSMT is almost 100 mm high. It commonly reaches a height of 50-60 mm (i.e. significantly larger than B. pulchra ) . It differs further from B. pulchra in its wider shape, wider varices with shorter, wider spines, its much less pronounced sutural channelling, its simpler and more widely spaced spiral threads over the varices, and its tendency to form smooth areas, lacking axial costae, over the central parts of the last two or three intervariceal intervals.

Biplex perca: Distribution. Throughout the Western Pacific archipelagoes, from central Honshu, Japan to northern Australia.
Although Biplex perca for many years was known only from southern Japan, and has been known by such common names as the "Japanese finned frog", this apparent restriction proves to result from the great intensity of sampling of Japanese coastal waters. The species is common in the Philippine Islands . Only one specimen of B. pulchra is present in MUSORSTOM 3 samples, and it is clear that B. perca is very much more abundant around the Philippines than is B. pulchra. The species appears to extend as far westward as Hong Kong. Although all previous more southerly records of large Biplex appear to have been of B. pulchra , the New Guinea specimen identified as G. aculeatum by HINTON (1978: 30, fig. 16) is B. perca , and several specimens in AMS and WAM are from Queensland. Australia and northern Western Australia (data listed above). The species occurs commonly in about 200 m or more throughout the western Pacific. No specimens in MNHN from New Caledonia are referred here with certainty.