URECHINIDAE 235 



high, the greatest height being behind the apical system. The frontal end is nearly 

 vertical, the frontal ambulacrum only slightly sunken. The labrum reaches the second 

 adjoining ambulacral plates ; two tube feet are found within the subanal fasciole. There 

 is a rather conspicuous fasciole along each side of the periproct. 



Since no Echinocardimn has hitherto been recorded from the West African coast 

 (south of Morocco) the discovery of this specimen is of considerable interest. It is most 

 desirable that further material of the species should be obtained in order that its identity 

 may be definitely settled. As it is a shallow-water species which no doubt lives buried in 

 sand or mud, it should not be difficult to collect it in sufficient numbers. 



Plagiobrissus sp. (young) 

 St. 279. 10. viii. 27. Off Cape Lopez, French Congo, 58-67 m. i specimen. 

 This young specimen, which is only 5 mm. long, seems almost certainly to belong 



to the genus Plagiobrissus, and quite probably it is Plagiobrissus Costae (Gasco). But it 



is too young to be definitely identified. 



From St. 933, 17. viii. 32, 260 m., there is a very young specimen of a Spatangoid 



which is quite unidentifiable ; the whole oral side is lacking, so that it is not even possible 



to see whether it is an amphisternous or a meridosternous form. 



Family URECHINIDAE 



Plexechinus Nordenskjoldi, Mortensen 



(Plate IX, figs. 5-7) 



Plexechinus Nordenskjoldi, Mortensen, 1910. Swedish South Polar Exped. Echinoidea, p. 61, 



pis. xvii, figs. 1-8; xviii, figs. 5-12. 

 P. A'ordenskjoldi, H. L. Clark, 1917. Hawaiian Echini. Echinoneidae . . . Spatangidae, p. 120. 



St. 27. 15. iii. 26. West Cumberland Bay, South Georgia, iiom. i specimen. 

 St. 140. 23. xii. 26. Stromness Harbour to Larsen Point, South Georgia, 122-136 m. 4 specimens. 

 St. 144. 5. i. 27. Off mouth of Stromness Harbour, South Georgia, 155-178 m. 2 specimens. 

 St. 148. 9. i. 27. Off Cape Saunders, South Georgia, 132-148 m. i specimen. 



These specimens in general agree very well with the type, as described in my work of 

 1910 ; but the oral side can scarcely be said to be " somewhat deepened " in front of the 

 peristome — there is hardly any depression at all to be observed here. Also it can hardly 

 be said that the mouth opening is "almost vertical"; it can at most be said to be dis- 

 tinctly oblique. The largest of the specimens is 19 mm. long, thus a good deal larger 

 than the type. 



In regard to the pedicellariae it is remarkable that ophicephalous pedicellariae are 

 lacking in all the present specimens ; on the other hand, the tridentate pedicellariae are 

 better developed, reaching a somewhat larger size than in the type (Plate IX, figs. 5-7). 



In some of the specimens a number of specimens of a Loxosoma are found attached 

 to the spines, mainly on the aboral side. 



This very interesting little Echinoid is still known only from the vicinity of South 

 Georgia. 



