372 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



consists of a single, almost rudimentary segment. The antennae differ 

 widely from any in the AselUdce, since they are less robust than the anten- 

 nulse, and but little longer; the peduncular segments are all short, having 

 almost the same proportion to each other as in Sphceroina (see pi. IX, 

 figs. 546 and 566), the last two being together about equal m length to the 

 first three, instead of far surpassing them as in the AseUidce; the flagel- 

 lum is short and few-jointed, mostly made up of a tapering basal seg- 

 ment, and not at all resembling the slender multiarticulate flagellum of 

 the Asellidw. The mandibles are adaptively modified in accordance 

 with the boring habits of the species, but the other mouth parts do not 

 seem to present characters from which comparisons need be drawn with 

 other families. 



The legs are somewhat similar to those seen in many AseUidce, being 

 furnished with short dactyli, each armed with a strong curved claw, and 

 a shorter spine below. A similar form of leg is, however, seen in S2)hce- 

 roma. The epimera are united to the lateral margins of the thoracic 

 segments almost precisely as in Sphwroma, an arrangement that does 

 not prevail in the AseUidce. 



The pleon has all its six segments well developed and perfectly separated 

 from each other, while in the AseUidce they are united into a single scuti- 

 form segment, or at most, the basal segment only is more or less distinct. 

 The pleopods are of the normal number and similar in form and texture 

 throughout ; the anterior pairs are ciliated. Each pair of pleopods consists 

 of a basal segment, bearing an inner narrow lamella and an outer oval one, 

 which, excej)t in the fifth pair, are well ciliated. In the male the inner la- 

 mella of the second pair bears, on its inner margin, a stylet, as in Spliceroma 

 and many other genera of Isopoda. In the AseUidce the branchial pleo- 

 pods are in fewer than five paii's, and are protected in front by a simple 

 or compound operculum of firmer texture than the other pleopods. Dr. 

 Coldstream * fell into an error in describing the respiratory organs as con- 

 sisting of "six pairs of scale-like bodies, pendant from the anterior seg- 

 ments of the tail, * * arranged in three rows, in an imbricated man- 

 ner, one of each kind ('oval' and 'nearly quadrangular') being articu- 

 lated together on a common peduncle on either side." He further 

 describes, loc. cit., p. 324, " two vesicular bodies of an oval form" behind 

 the branchiae. These organs were without doubt the external lamellae 

 of the fifth pair of pleopods, as shown by his figure. There are, how- 

 ever, four instead of three ciliated pairs anterior to the last pair, one 

 of which was overlooked by Dr. Coldstream, and in this error he has 

 been followed by Bate and Westwood. t If the observations of Dr. Cold- 

 stream had been correct, an afQnity might have been indicated with the 

 AseUidce. The terminal segment is flattened and scutiform, in shape 

 resembling that of Jccra, but the uropods are strictly lateral, being 

 attached at the broadest part of tlie segment and in front of the middle. 



* Edinburgh New Phil. Journal, vol. xvl, p. 323. 

 t Brit. Sessile-Eyed Crustacea, vol. ii, p. 350. 



