PONTOGENEIIDAE 195 



5. St. 175. South Shetlands. 1 c? 18 mm., 19 $$ 16-18 mm., 1 ovig. $ 20 mm. 

 Four mutilated specimens. 



6. St. 181. Palmer Archipelago. 10 9? 12-20 mm. 



7. St. 182. Palmer Archipelago. 1 ? 16 mm. 



8. St. 187. Palmer Archipelago. 16*11 mm., 1 ovig. $15 mm. 



9. St. 190. Palmer Archipelago (315 m.). 2 6*6* 17 mm., 1 $ 15 mm. (somewhat 

 mutilated). 



Description. Close to inflata (Sars) but: pleon segments 1-4 tricarinate, all the 

 carinae produced into small acute teeth except the medio-dorsal one on segment 3, and 

 the dorso-lateral ones on segment 4 ; and telson cleft for not more than, or scarcely more 

 than (St. 51), one-third its length. 



Remarks. The much larger size and the fact that pleon segment 4 is tricarinate as 

 well as the preceding three segments distinguishes this species from its northern 

 counterpart inflata. From rostrata (Bonn.) it differs in having dorso-lateral keels on 

 pleon segment 1 as well as on the three following segments, and well- developed eyes. 



The smaller specimens from St. 51 do not appear to differ in any way from the others 

 except in the slightly deeper telsonic cleft. 



Family PONTOGENEIIDAE 



Stebbing, 1906, pp. 356, 729. 



Schellenberg, 1929 a, p. 273 (revision, with key to genera). 



The representatives of this family have hitherto been involved in considerable con- 

 fusion, and we have to thank Schellenberg for a most useful revision with sharp 

 delimitations of the various genera. But, needless to add, many of the earlier species 

 are still obscure, and only an examination of material collected in the original localities, 

 and a re-examination of the material collected by previous expeditions, will extricate 

 and stabilise the synonymy. 



Chilton, relying apparently too implicitly on the assumption of "widely distributed 

 species", did much to confuse our knowledge of the distribution of the species of this 

 family by erroneous identifications. It is greatly to be regretted that, e.g., the Scotia 

 material must be entirely re-examined before the localities there recorded can be 

 available for working out the distribution of the species. 



In suggesting the use of one character which has only been employed previously in 

 a few cases, no generic value is claimed for it, though it would seem to have considerable 

 specific value. This character is the surface sculpturing of the integument. From the 

 figures here given for all the species contained in the Discovery collection, it will be 

 seen that the differences are of no mean order and may well be used to separate species, 

 or per contra as an indication of affinity. 



It is in fact rather extraordinary that so little attention has been paid to the surface 

 of the integument, apart from major features such as knobs, teeth, spinous processes and 

 the like. The surface sculpture has been used to differentiate the species of Hippomedon 

 (cf. Sars, 1895, pis. xx, xxi and Stephensen, 1923) and has been mentioned casually 



