1 6 BULLETIN OF THE LABORATORIES 



are exactly as in /. agilis, having two small basal spines and a few 

 sharp serrations near tlie apex, anteriorly. Near the base of the claw 

 is a cluster of small spines of two sizes, then begins a series of about 

 sixteen lateral teeth averaging 0.02 mm. in length and extending to 

 the sides of the anus. Above this point the contour of the margin is 

 convex and is ornamented with nine spines twice as long as the pre- 

 ceding. Then follow the prominences which bear the long and sim- 

 ple caudal setae. Besides the above mentioned spines there are four 

 spines on either side upon the lower posterior angle of the post-abdo- 

 men which are four times as long as those of the previously men- 

 tioned continuous series (i. e. 0.08 mm.) .\bove the abdomen is 

 hirsute or thorny as in /. agilis, and the process for closing the brood 

 sac is similar. It will be seen that the post-abdomen differs in arma- 

 ture as much as in form from the other species. From /. sordidus it 

 differs in the following points : The claws are not pectinate behind, 

 but are serrate in front, the anal opening is higher and the details of 

 the spines vary ; from /. acutifroiis it differs in that the claws are not 

 pectinate, neither is there a spine in front of the claws, and the anus 

 is not terminal ; from /. agdis it differs, in that the shape is different, 

 there are fewer enlarged spines, and the shape of the nine spines 

 above the anus is different. The head is convex, resembling /. sor- 

 didus most nearly, but the antennules are much longer and more slen- 

 der than in any other known species. They are 0.17 long and about 

 0.016 mm. wide, while the longest seta is 0.084 ^o^^g- The antennae 

 are almost exactly as in /. sordidus. The labrum has the usual shape, 

 as have the jaws and other appendages. The margins of the shells 

 are ornamented with spines simply pectinate or barbed, as in /. agilis. 

 In /. sordidus these spines are variously branched and in that form 

 alone of the European species, according to Kurz, is there a failure to 

 perfect the moult ; in our species, which has simply pectinate setae, 

 the old coverings are all but uniformly retained. The spines of the 

 lower posterior margin are from 0.16 mm. to 0.20 mm. long." 



Since we have a full description of Ilyocryptus spinifer, Herrick, 

 we have the data for deciding whether it is identical with Ilyocryptus 

 longiremus, Sars, or not. To facilitate the comparison the following 

 table has been comj)iled. The characteristics of /. longiretnus are taken 

 from Professor Birge's description and illustr: tion. The characteris- 

 tics of /. spinifer are taken from the above cjuotation and the illustra- 

 tions which accompany it. 



