32 FOSSIL ECHINI OF THE WEST INDIES. 



Genus CLYPEASTER Lamarck, 1801. 



Type species. Echinus rosaceus Linne, l758,Syst.Nat.,ed. 10, p. 665. 



The genus Clypeaster is represented by many species, 19 occurring 

 fossil in the fauna of the West Indies. The species have so much 

 variation, and the characters of different species run so close, that 

 Doctor Clark's expert opinion in diagnosing them has been of the great- 

 est value in describing the material and arriving at conclusions as to 

 what should be considered as distinct species. 



Many fossil species have been described by Cotteau and other 

 authors from this region, but it has been found necessary to add 5 

 new ones to include material that could not find a place in those already 

 described. On account of the closeness and difficulty of identifying 

 species of Clypeaster, I have given under each species the essential 

 diagnostic characters, even where there were no available specimens. 



Key to the West Indian Fossil Species of Clypeaster. 



] . Oral surface of the test deeply concave. 



A . Poriferous areas of petals more or less incurved at tip, often nearly or quite closing 

 petal; if petals are widely open, the interporiferous area is broadly 

 obovate. 

 B. Petals more or less obovate; interporiferous area near proximal end only about 



half as wide as it is where widest. 

 C. Mouth and apical system approximately central. 

 D. Width of test 85 per cent of length, or less. 



E. Test not excessively arched nor interporiferous areas remarkably swollen. 



F. Petals more or less widely open C. rosaceus 



FF. Petals more or less nearly closed. 



G. Test with a more or less evident flat area, distal to petals; poriferous 

 areas, especially of petals II and IV, rather markedly wider near 

 tips, which bend in somewhat abruptly and nearly meet. . . . C. concavus 

 GG. Test more uniformly arched, with no flattened area distal to petals; 

 poriferous areas not markedly widened near tips, which, after 

 bending inwards, turn abruptly outwards and run parallel for a 



short distance C. caudatus 



EE. Test excessively arched and interporiferous areas remarkably swollen.. C. dalli 



DD. Width of test 90 per cent of length, or more C. cubensis 



CC. Apical system distinctly excentric posteriorly, mouth perhaps posterior; 



petals very large, posterior pair reaching nearly to the ambitus.. C. parr a 

 BB. Petals long, elliptical; interporiferous areas not twice as wide distally, or near 



middle as proximally. 



H. Test narrow anteriorly, its width just in front of petals II and IV 

 about 70 per cent of length; petaloid area small, its length about 

 60 per cent of test length; tips of petals II and IV nearly closed 



and rather abruptly so, as though pinched together C. lanceolatus 



HH. Test in front of petals II and IV with width about 80 per cent of 

 length; petaloid area large; with its length about 70 per cent of 

 test length; tips of petals II and IV more or less widely open.. C. antillarum 

 A A . Poriferous areas of petals not strongly incurved at tip; petals widely open. 

 /. Petals rounded and poriferous areas incurved at tip, at least a little. 

 J. Sides of interporiferous areas convex, converging slightly near tip. 



K. Petals all marked with distinct furrows connecting the pores of a pair, test 



more or less arched ; test margin moderately thin C. planipetalus 



KK. Petals very indistinct, with furrows connecting pore-pairs shallow, or nearly 



wanting; test flat with very thick margin C. cryptopetalus 



JJ. Sides of interporiferous areas nearly or quite straight and even a little diverging 



in some cases C. cotteaui 



II. Petals truncate and poriferous areas more or less so. 



L. Petaloid area two-thirds of test length C. batheri 



LL. Petaloid area distinctly more than two-thirds of test length C. parvus 



