210 DR. C. CHJLTON ON THE SUBTEREANEAN 



with Norman and Stebbing's descriptions ; but even this must be considered merely 

 provisional, as only the one species is known, and nothing is known of the distinctive 

 characters of the two sexes : — 



Eyes wanting. Segments of the pleon separate (in both sexes ?). Both pairs of 

 antennae without distinct fiagella (in adults ?). Mandibles without palp. Maxillipedes 

 not divided into separate joints. Last segment of the peraeon small and without 

 appendages (in adults ?). 



All the specimens that I have seen, many scores in number, agree in having the 

 seventh segment of the perseon small and without appendages ; but as I have never seen 

 a specimen that I could be certain was sexually mature, I am doubtful whether this 

 character would hold in the adult also or not. My specimens have been obtained from 

 several wells in different localities, and were collected at different times during a period 

 of about ten years, and it seems scarcely likely that all the specimens should be immature, 

 and tliat during the Avhole time not a single mature specimen should be obtained, unless, 

 indeed, the adult differs from the immature form in habits in such a way as to prevent it 

 being liable to be drawn up by the pump. I have one specimen that has the integument 

 of the under surface of the peraeon much expanded, somewhat in the same way as shown 

 by Stebbing in his figure of the "gravid female" of Parantlmra n>.gro-2mnctata [106, 

 pi. xxvi. fig. ii. D, ? ] ; but in my specimen I can discover no trace of eggs or young, and 

 it appears to be the integument itself that is distended, and not a pouch formed by 

 brood-plates attached to the bases of the legs in the usual way ; so that I am uncertain 

 whether this specimen is really an adult female or is abnormal in some way, owing 

 perhaps to half-completed ecdysis or some similar cause. 



All this uncertainty makes comparison of Cruregcns with other genera of the 

 Anthuridae a very difhcult task, but it appears to approach to Faranthura more nearly 

 than to any other. It resembles this genus generally in the antennae (leaving out of 

 consideration the special brush-like antenna of the adult male in Faranthura), in the 

 perseon and its appendages, and in the pleon and the jileopoda, though the uropoda are 

 much more slender in Cruregens. It differs, however, in the mouth-parts, for the 

 mandibles have no palp and the maxillipedes have lost all trace of separate joints. If 

 the absence of tlie seventh pair of legs is a character that holds in adults, this would 

 form another difference between the two genera. 



It is to be noted that the seventh pair of legs appears to be developed at a later period 

 of the life-history in the Antlmridae than in other Isopoda, for specimens without them, 

 but apjoarently mature in other respects, are not infrequently met with. Besides 

 Cruregens we have the following examples : — Hi/ssiira producia is founded on a single 

 specimen about a quarter of an inch long, of which Stebbing and Norman say " the last 

 segment of the peracon in the type specimen has no legs, nor can we see any sign of scars 

 where they would have been attached, and the specimen was otherwise quite jjerfect " 

 [106, p. 128] ; Faranthura neglecta, Beddard, is said to have the seventh segment of the 

 pcrseon absent, the specimen is 6 millim. long, and from the absence of the last pair of 

 legs Beddard considers it to be immature, though he does not mention any other point of 

 immaturity about it [9, p. 114.] ; I have also a small specimen of an Anthurid from Port 



