Verrill, JVotes on Eodlata. 571 



to -10 ; transverse diameter of mouth 1-03 ; longitudinal diameter -25 ; 

 its largest plates '15 to -25 ; medium siz^d plates -10 to -12. Another 

 specimen is ooO inches long; 4-30 broad; 1-85 high. A small speci- 

 men, distorted above, is 4-1 S 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, west coast of Africa,— Rev. D. W. Burton. 



This species is closely allied to F. pectordis Ag., from Florida and 

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

 tioned in the published descriptions, are here added. 



Plagionotns pectoralis Agassiz aud Desor. 



Spatangus pedoralis Lamarck, Hist. an. sans vert., iii, p. 383; Desmoulius, Eehin.. p. 

 3811. 



Brisms pectoralis Agassiz. Prodromns, p. 184. 



Biiss>j,.s (Plagio lotus) pectoralis Ag. and Des., Cat. Rais., Ann. des Sei. mt, viii, p. 

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



Plagionotns pect'>ralii Gray, Cat. Ech. Brit. Mas3U'n, p. 50, 185.j ; A. A.;assiz, Bul- 

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



Plagionotus Desor ii G-ray. 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 ditferences. 



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

 often comparatively acute, rising with a gradual slope on all parts, 

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

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

 nate, with the anterior ambulacrum more sunken. The anterior 

 lateral and posterior 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. Tiie large tubercles are quite variable in number in P. 

 2)ectoraUs^ 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 interambulacra next to the anterior ambulacral zone, which 

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

 smaller in the former. The peripetalous fasciole is broader 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 



