SYSTEMATIC DESCRIPTIONS — CLYPEASTRINA. 33 



Key to West Indian Fossil Species of Clypeaster — Continued. 



2. Oral surface of test slightly concave or flat, with mouth more or less sunken. 

 M . Test convex, sloping upward more or less uniformly from the thick margin. 



N. Height of test equal to or exceeding one-half its width C. duchassaingi 



AW. Height of test not more than one-third its width C. ambigenus 



MM. Test flattened; if petaloid area is elevated, it does not slope upward evenly 

 from margin. 

 O. Test with thin, uniformly sloping margin. 



P. Test very flat, with flush petaloid area C, placenloides 



PP. Test not flat, its petaloid area conspicuously elevated C. meridanensis 



OO. Test with very thick, more or less swollen margins. 



Q. Oral surface distinctly concave C. oxybaphon 



QQ. Oral surface perfectly flat C. platygaster 



Clypeaster rosaceus (Linne). 



Echinus rosaceus Linne, 1758, Syst. Nat., ed. 10, p. 665. 



Clypeaster rosaceus Lamarck, 1801, Anim. sans Vert., p. 349. Cotteau, 1897, Bol. Com. 



Mapa Geol. Espafia, vol. 22, p. 29, plate 5, figs. 1 to 5. Lambert, 1915, Mem. Soc. 



d'Agric. de I'Aube (Troyes), vol. 79, p. 19. 



The following is a description of this species : 



This well-known living species, occurring abundantly in the Recent 

 fauna of the West Indies, also occurs fossil in the same region. Test very 

 large, pentagonal in outline, the sides and posterior end being somewhat 

 concave, the anterior end bluntly pointed, and margin thick. The upper 

 surface is convex, very variable in the height and width of the test, but 

 Dr. H. L. Clark says he has never seen a specimen in which the width 

 equaled 85 per cent of the length. The under surface is flat near the margin, 

 but deeply concave to the peristomal opening. The ambulacral petals 

 are very broad, usually strongly elevated. The interporiferous area is 

 almost always markedly obovate, especially in the anterior petals II and 

 IV. In the poriferous areas there are 6 to 9 primary tubercles on the ridges 

 between the pore-pairs. The interambulacral areas are very narrow, espe- 

 cially at the margin. Apical disk is central, peristome pentagonal, central, 

 at the bottom of the deep central cavity; periproct small on the ventral 

 side, but near the posterior border of the test. 



A very fine large specimen, collected by Mr. Mitchell in Porto Rico, 

 gives the following measurements: height, 45 mm.; length through 

 ambulacrum III and interambulacrum 5, 132 mm.; width, 107 mm. 



This species seems to be peculiar in its distribution as a fossil. It is 

 quite abundant in Porto Rico and is reported by Cotteau from Cuba, 

 but excepting Lambert's I do not know of definite records of fossil 

 material from other islands of the West Indies. It is such a 

 massive, solid species it should have been preserved if it had occurred. 



Desor (1858, Synopsis des Echinides, p. 244) notes that rosaceus 

 occurs fossil and says "Des Antilles et de la Guadeloupe. Tres abon- 

 dant." It seems that this has reference, however, to the abundance of 

 the living form in that region rather than as a definite locality for the 

 fossil. He gives the name Clypeaster incurvatus Desmoulins (which is 

 a nomen nudum) as a synonym of C. rosaceus. 



