SYSTEMATIC DESCRIPTIONS SPATANGINA. 



Anguilla, T. W. Vaughan collector, 2 specimens, U. S. Geol. Sur. station 

 6894. Crocus Bay Bluff, southwest side, uppermost horizon, 125 feet 

 above sea-level, mostly limestone, Anguilla, T. W. Vaughan collector, 

 1 specimen, U. S. Geol. Sur. station 6967. Cevicos limestone, Arroyo 

 La Mora, west of Cevicos, Dominican Republic, C. W. Cooke collector, 

 1 specimen, U. S. Geol. Sur. station 8599. 



Genus PLAGIOBRISSUS Pomel, 1883. 



Type species. Spatangus pectoralis Lamarck, 1816, Anim. sans 

 Vert., vol. 3, p. 29 Echinus grandis Gmelin, 1788, Linne, Syst. Nat., 

 ed. 13, vol. 1, part 6, p. 3200. 



Cotteau calls his species Plagionotus loveni, but Plagionotus as a 

 generic name is not available for Echini and Pomel's substitute Plagio- 

 brissus must be used (see H. L. Clark, 1917, Mem. Mus. Comp. Zool., 

 vol. 46, p. 207). Clark considers that the group of Echini distinguished 

 under the name Plagiobrissus is rightfully separated from Metalia, as 

 it not only differs from that genus structurally, but its geographical 

 distribution is wholly different. Metalia is an Indo-Pacific genus, while 

 Plagiobrissus is confined to certain parts of the tropical Atlantic and 

 the western Mediterranean. Louis Agassiz first distinguished the group, 

 but his generic name Plagionotus being preoccupied, A. Agassiz, in the 

 Revision, simply merged the component species with Metalia of Gray, 

 which is the most nearly allied genus. There the matter has rested, 

 excepting that Pomel, in his remarkable but generally ignored work, 

 suggested the name Plagiobrissus as a substitute for the preoccupied 



Plagionotus. 



Plagiobrissus loveni (Cotteau). 



(Plate 14, Figure 5.) 



Plagionotus loveni Cotteau, Kongl. Sven. Vet. Akad. Handl., vol. 13, No. 6, p. 41, plate 8, 

 figs. 7, 8. 



The following is an extract from the original description of this species : 



Species of large size, cordiform, rounded and strongly indented anteriorly, 

 a little acuminate posteriorly. Upper face moderately swollen. Apical 

 disk excentric anteriorly. Anterior furrow nearly wanting on approaching 

 the apical disk; very pronounced toward the ambitus. Anterior ambu- 

 lacrum III straight, with small rounded pores. The paired ambulacral 

 petals are narrow, long, excavated, especially in the upper part, nearly 

 superficial in approaching the ambitus. Poriferous areas are wide, with 

 oblong transverse pores united by a furrow, alternating with small granular 

 bands. The interporiferous areas are furnished with small tubercles, unequal 

 in size and scattered ; these areas are of nearly the same width as one of the 

 poriferous areas. Tubercles are of two kinds, one very large, crenulate, 

 and perforate, surrounded by a large scrobicule, unequal and scattered; 

 these occupy a large part of the dorsal region, descending nearly to the 

 ambitus, but clearly limited by the peripetalous fascicle. The other kind 

 of tubercles are much smaller, crowded, and very abundant, filling the 

 spaces between the large tubercles. Below the peripetalous fascicle and 

 as far as the ambitus these smaller tubercles are very fine, crowded, per- 



