372 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



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

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

 nulse, and but little longer 5 the peduncular segments are all short, having 

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

 figs. 54 b and 5Q &), the last two being together about equal in length to the 

 first three, instead of far surpassing them as in the AselUdce; 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 AseUidiv. The mandibles are adaptively modified in accordance 

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

 seem to present characters from which comparison!^ need be drawn with 

 other families. 



The legs- are somewhat similar to those seen in many AselUdce, 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 Sphw- 

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

 segments almost j)recisely as in SSjiluvroma, an arrangement that does 

 not i^revail in the AselUdce. 



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

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

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

 The lileopods 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, except 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 8ph(eroma 

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

 pods are in fewer than five pairs, 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 pan*, 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 affinity might have been indicated with the 

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

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

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



* Edinbvirgli New Phil. Journal, vol. xvi, p. 323. 

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



