SYSTEMATIC DESCRIPTIONS — HOLECTYPINA. 27 



IRREGULAR OR EXOCYCLIC ECHINI. 

 THE EXOCYCLOIDA. 



While the regular or endocyclic Echini occurring fossil in the West 

 Indies are very rare for the most part and represented by but very 

 few species outside of the Cidaridae, on the other hand the exocyclic 

 Echini are abundant in species and often in individuals. With but 

 few holectypoids, the clypeastroids are abundant in species and in- 

 dividuals, and there are many species of spatangoids. 



Clypeastroids usually have thick, solid tests well adapted for pre- 

 servation as fossils; but spatangoids, on the other hand, often have 

 thin, delicate tests which, as fossils, are frequently crushed beyond 

 recognition. 



Key to the West Indian Fossil Suborders of Exocycloida. 

 Peristome central, jaws present. 



Ambulacral plates compound or largely simple, areas non-petaloid dorsally; ambitus 



oval or circular, but test when circular is not discoidal Holectypina 



Ambulacral plates simple, areas petaloid dorsally; when the ambitus is circular the 



test is discoidal Clypeastrina 



Peristome eccentric, without jaws Spatangina 



The Holectypina are represented in the fossil West Indian fauna 

 by only 3 genera and the same number of species. The Clypeastrina 

 are represented by 8 genera and numerous species. The Spatangina 

 are represented by 19 genera and numerous species. 



Order EXOCYCLOIDA Jackson, 1912. 



Suborder HOLECTYPINA Gregory, 1900. 



Key to the West Indian Fossil Species of Holectypina. 



Ambitus oval; periproct marginal or supramarginal Conulus antillensis 



Ambitus circular; periproct on oral surface. 



Test high, vertical diameter not much less than horizontal diameter; periproct 



broadly oval. Genital 2 much larger than other genitals .... Lanieria lanieri 

 Test depressed, vertical diameter only about 60 per cent of horizontal diameter; 

 periproct narrowly elliptical. Genital 2 not much larger than other 

 genitals Discoidea decorato 



Genus CONULUS Leske, 1778. 

 Type species. — Conulus albogalerus Leske, 1778, Add. ad Klein, p. 98. 

 The name Echinoconus, a pre-Linnsean name, gives way to Conulus 

 Leske, which is the name first used after Linnaeus. Galerites of Lamarck 

 is the same thing, but is a later name than Conulus and therefore be- 

 comes a synonym. 



Conulus antillensis (Cotteau). 



Echinoconus antillensis Cotteau, 1881, Ann. Soc. Geol. Belgique, vol. 9, p. 13, plate 2, figs. 

 1, 2; 1897, Bol. Com. Mapa Geol. Espana, vol. 22, p. 21, plate 3, figs. 1, 2. 



Cotteau says that this species is known only from a single specimen, 

 which he attributes to the Cretaceous. Cienfuegos, Cuba, collection 

 of M. Moens, in Lede. 



