NO. 1876. ON TEE CRUSTACEAN ORDER CUMACEA—CALMAN. 



665 



Fig. 88.— Diastylopsis 



DAWS0N7, niMATURE 

 FEMALE, THIRD LEG. 



the antero-lateral tooth; the anterior part of the lower margin is 

 finely serrated. The ocular lobe is shghtly swollen, but there is no 

 pigment and the visual elements are not distinctly visible. 



The free thoracic somites together are about two-thirds as long as 

 the carapace. The pleural plates of the second 

 somite are concealed beneath those of the tliird. 

 The pleural plates of the tliird and fourth somites 

 are not so strongly produced backwards as in the 

 female and the length of both together is just about 

 one-half that of the carapace. 'There is no marked 

 interval between the second and tliird pairs of legs. 

 The last thoracic somite probably bears a pair of 

 short curved sternal teeth as in the female, but 

 only one remains in the specimen examined. The 

 first abdominal somite has a single large curved 

 sternal tooth anteriorly and the first and second 

 have each a lateral tooth external to the attachment 

 of the pleopods. The telson is about as long as the last somite and 

 dorsally humped. There are some nine pairs of setiform lateral spines. 

 The tliird segment of the peduncle of the antennule is nearly as 

 stout as the preceding and bears a terminal brush of fine hairs. The 

 flagella are much longer than in the female, the major 

 flagellum having four or five segments. 



The flagellum of the antenna extends to the tip of 

 the uropods. 



The legs appear not to differ greatly from those of 

 the female except in the presence of exopods on all 

 except the last pair. The ischium of the penultimate 

 pair has a conspicuous tooth posteriorly. 



The uropods resemble those of the female, but the 

 spines on the inner edge of the endopod and peduncle 

 are more numerous and pectinated. 



Remarks. — Of tliis species, the genotype of the genus 

 Diastylopsis, no figures have hitherto been pubUshed. 

 The specimens examined agree so well with Smith's 

 description, however, that there can be no doubt of 

 their specific identity. Of the other species referred 

 to the germs, D.thileniusi Zimmer^ apparently comes 

 nearest to the type, but is distinguished from it, 

 among many other characters, by the remarkable structure of the 

 third maxilhpeds, on which I have already commented.^ A closely 

 similar modification of the third maxillipeds is found in Mr. Steb- 

 bing's genus Dic.^ 



1 Zool. Jahrb. Syst., vol. 17, 1902, p. 449, text figs. 

 3 Ann. Mag. Nat. Hist., ser. 8, vol. 1, 1908, p. 239. 

 8 Ann. S. Air. Mus., vol. 6, 1910, p. 415, pi. 47. 



Fig. 89.— Dlasttlop- 

 sis dawsoni, im- 

 mature female, 

 last somite, tel- 

 son, and uropod. 



