406 Proceedings of the Royal Physical Society. 



"Plates of the corona only slightly overlapping, and forming a 

 continuous shell without membranous interspaces. Ambulacral 

 and interambulacral areas of the apical surface of the test with 

 irregular rows of primary tubercles with small areolae. Oral 

 surface of the test different in character from the apical, with the 

 areolae of the primary spines large and deep, occupying a large 

 portion of the surface both of the interambulacral and of the 

 ambulacral plates" (Wyville Thomson). 



3. Phormosoma placenta, Wyville Thomson. 



1874. Phormosoma placenta, Wyv. Thomson, "Porcupine" Echin,, 



Phil. Trans., p. 745, pi. Ixii. ; pi. Ixiii., 



figs. 1-8. 

 1883. ,, ,, Agassiz, "Blake" Echini, Mem. Mus 



Comp. Zool., X., p. 30, pi. xii.; pi. xv., 



figs. 3-19. 

 1889. ,, ,, Bell, Ann. and Mag. Nat. Hist., (6) iv., 



pp. 436-438. 



Diagnosis. 

 This species is remarkable for the large tubercles of the actinal 

 surface, occupying the greater part of the ambulacral and inter- 

 ambulacral plates. 



Distribution. 



British Seas. — N.-W. of Lewis, warm area, "Porcupine" (1869), 

 St. 90, 458 fms. (Thomson, 1, 2). " Knight Errant," St. 4, 555 

 fms. ; St. 7, 530 fms. (A.GASSIZ, 4). "West of Scotland and Ireland, 

 500-800 fms. (Thomson, 2). S.-W. Coast of Ireland, 1000 fms. 

 (Bell, 3). 



Other Localities. — Coast of U.S.A., 458-1309 fms. (Yerrill). 

 Lesser Antilles, 154-1242 fms. (Agassiz, 5). 



4. Phormosoma uranus, Wyville Thomson. 



1877. Phoimosoma uranus, Wyv. Thomson, The Voyage of the 



«' Challenger"; The Atlantic, i.,p. 146, 

 figs. 33, 34. 



1880. ,, Petersii, Agassiz, Bull. Mus. Comp. Zool., viii., 



p. 76. 



1881. ,, uranuSf Agassiz, "Challenger" Echin., p. 103, 



pi. xviiic, fig. 12. 

 1883. ,, ,, Agassiz, "Blake" Echini, Mem. Mus. 



Comp. Zool., X., p. 35, pis. x., xi. 



