To this genus Polycheks Heller now, of which Pol. typhlops is the type species, 17 

 species must be assigned and it is my firm conviction that in all these forms the thoracic legs, 

 except the last pair, are provided with normal epipods, which, however, may vary in length; 

 the epipod of the external maxillipeds in most cases is also normally developed, sometimes it 

 is of fair size, sometimes small and slender, while only in Pol. Taiincri I""ax. it is reduced to 

 a mere rudiment. In the following 9 species the external maxillipeds and the first four thoracic 

 legs are provided with normal epipods: baccatus Sp. Bate, Carpenteri (Alcock), etithrix (Will.- 

 Suhm), giddus (Alcock), gracilis (Sp. Bate), grantdattis Fax., laevis (Sp. Bate), obsc7trits (Sp. 

 Bate) and typhlops Heller. In Pol. Tanneri Fax. the epipods of the thoracic legs are about 

 half as long as their podobranchs, though very delicate in texture, while that of the external 

 maxillipeds is a mere rudiment. Pol. asper Rathb., crucifer (Will.-Suhm) and Snydcri Rathb. 

 bear an epipod on the e.xternal maxillipeds, but those of the thoracic legs have not been 

 described. Unfortunately also nothing is known about the epipods of Pol. debilis (S. I. Smith), 

 debilis (S. I. Smith) var. aruiata Bouv., ilnbins Bouv., eryoniforinis Bouv. and validus (A. M.- 

 Edw.). It would appear therefore doubtful whether the last mentioned species are indeed congeneric 

 with the preceding ones, the epipods of which have been described, but the species of this 

 genus show still other features that are common to all. The lateral borders of the carapace, 

 namely, are constantly armed with more than 20 spines: the smallest number, 21 or 22, 

 are observed in Pol. Tannci'i Fax., 46 to 48 occur in Pol. Snydcri Rathb. and 51 to 54, which 

 is the largest number known, even in Pol. aspcr Rathb., while one observes an intermediate 

 number in the other species. The only exception is presented by Pol. obscurits (Sp. Bate), in 

 which form the lateral margins are armed with 11 to 13 spines : the specimen, however, on 

 which this species has been founded, was only 25 mm. long, probably still young and, as we 

 read in the Challenger Report, was "in a very poor condition and had much the appearance 

 of one that had recently cast its skin". 



In the second place the median dorsal carina of the carapace is usually double, granulated, 

 rarely nodulated and in most cases presents no definite small number of spines, being often 

 traversed by bead-like tubercles or granulations or covered with crowded spinules. The i^' 

 abdominal tergum, finally, is probably never armed with the two small spines at and near the 

 outer ends of the anterior border, that generally occur in the species of Stereoinastis. 



The genus Stercomastis Sp. Bate now contains at jaresent 10 species. In these species 

 the epipod of the external maxillipeds has been described as rudimentary [auriculata (Sp. Bate), 

 Stihmi (Sp. Bate)), very minute [iiayia (S. I. Smith)) or as represented at most by a papilla 

 (andamancnsis (Alcock), ccrata (Alcock), phosphorus (Alcock), scnlpta (S. I. Smith), sculpta 

 (S. I. Smith) var. pacifica Fax. and trispinosa (de Man)). In these last mentioned five species 

 and variety the epipods of the thoracic legs are membranous expansions of the base of the 

 podobranchs; this is also the case with Stereojjt. Suhini (Sp. Bate), according to the fig. 38, 

 page 158, of the Challenger Report, while in Stercoin. miriculata (Sp. Bate) the epipods are said 

 to be absent from the thoracic legs. As regards Stereom. Helleri (Sp. Bate) I would remark 

 that of the type specimen, which was a male and collected at Stat. 218 of the Challenger 

 Expedition, North of New Guinea, the epipods have not been described, while the specimen 



