VerriU, JVotes on Radiata. 571 



to "10 ; transverss diameter of imuth 1-03 ; longitudinal diameter -25 ; 

 its large.^u platen -15 to -Ic, ; me limn siv:jd plates -10 to •12. Another 

 specimen is o'oO inches long; 4*30 broal; TSo high. A small speci- 

 men, distorted above, is 4*18 inches long; 3-30 wide; 1'95 high; acti- 

 nal area "60 wide; "23 long. In this the inner plates of the actinal 

 area are smaller and more numerous. 



Sherbro Island, wo^t coast of Africa, — Rev. D. W. Burton. 



This species is closely allied to P. pvitor ills Ag., from Florida and 

 the West Indies. For the sake of comparison some details, not men- 

 tioned in the published descriptions, are here added. 



PlagionotUS pectoralis Agassiz and Desor. 



Spatangus pedoralis Lamarck, Hist. an. sans vert., iii, p. 383; Desmonlins, Echin.. p. 

 38'). 



Brissus pectoralis Agassiz. Prodronius, p. 184. 



Brissiis [Plagio lotus) pactoralls Ag. and Des., Cat. Rais., Ann. des Si-i. u it, viii, p. 

 13, 1847; vi, Tab. 16. fig. 15. 



Plagionotu'i pect'tralii Gray, Cat. Bcli. B.'it. Mus3un, n. 50, 1855; A. A>4'ass'z, Bul- 

 letin Mas. Comp Zool. I, p. 275, 1870. 



PlagionotUS Desorii Gray. op. cit., p. 51. 



Several West Indian specimens of this species, of various sizes, 

 which I have had opportunities to compare with the African speci- 

 mens, present the following differences. 



The test is much more depressed, the margin less elevated and 

 often comparatively acute, rising with a gradual si jpe on all parts, 

 except at the posterior end. The outline is also more regularly 

 ellijitical, with rounded sides; the anterior end is more deeply emargi- 

 nate, with the anterior ambulacrum more sunken. The anterior 

 lateral and posteiior ambulacral petals are longer and narrower, with 

 the sides parallel for a great part of the length, and they are less di- 

 vergent, being directed at first more anteriorly and posteriorly, but 

 are more strongly recurved toward the outer ends ; this renders the 

 lateral interambulacra broader and the anterior and posterior ones 

 narrower. The large tubercles are quite variable in number in P. 

 pectoralis^ but are often more numerous, though not usually arranged 

 in such regular rows. In all the specimens of the latter, which I have 

 seen, there are no large tubercles on the triangular area of the an- 

 terior interambulaci'a next to the anterior ambulacral zone, which 

 bears large tubercles in P. Afrleanus. The small tubercles are 

 smaller in the former. The peripetalous fasciole is bi-oader in P. pec- 

 toralis ; and the plastron is longer and more oblong, with the sides 

 more nearly parallel. The anal area is smaller, ovate, the upper 



