RerBr''S .- Several vnlves bel orio-ing to this species are in 

 the oollections at hand, the largest having the follovTinn rliTnen- 

 sions: length 47.5 nmi. ; "1~., ^8 nim. ; ;-'"rniaiam. , 11.8 ma. i'he 

 shell is slightlv depressed in front of the posterior carina, hut 

 not enoiieh to affect the margin. 3etv.-een the carina and the es- 

 cutcheon is another fainter carina; midway oetween the tv70 carinae 

 is a faint, shallow sul n the ventral half of the shell. The 



relative v/idth of the limnle and esoiitcheon is inconstant, hut in 

 length they are snbequal and the Iminle is usually more deeply 

 ipresse"!, On the. largest valve the concentric undulations are 

 somewhat irrogiils r on the ventral half of the anterior slope. 



2. :amaicen!jis is disting-iished "by its sub equilateral outline 

 and the presence of concentric undulations in the umhonal region 

 and on the anterior slope. D^]l has f'escrihed a very closely re- 

 lated s-oecies from the Ohipola r.iarl- J_« chipolanus il]i The typi- 



(1). loc. cit., p. 147?;, pi. 49, fi?-. 1?,, 190."^. 



eal Ohipola form -differs in having fine coii-^entric undulations 

 on the entire snvzi _, ----ce-ot on the posterior slope. This con- 

 centric sculptiire niay be obsolete or may be "present on only the 

 anterior third or less of the shell. 3uch forrns are "Ufr'erentiat- 

 ed from j ama i c e ri o i p. b ' "i-nvT- c- fT^.m ^~"^ ^'^ -f'liri- yc.-r-^- n'-i'^r-ce undula— 



