56 FOSSIL ECHINI OF THE WEST INDIES. 



original number of "Y. 5," which is the number given by Desor as 

 the type of the species. It is from the Louis Agassiz collection, which 

 was received at the Museum of Comparative Zoology in 1859. Duncan 

 and Sladen (1883, Palaeontologia Indica, ser. 14, p. 13) publish some 

 notes on the species based on a specimen in the British Museum. 



This species closely resembles Aniblypygus merrilli Twitchell (1915, 

 Monograph U. S. Geol. Sur., vol. 54, p. 165, pis. 76, 77, 78, figs, la 

 to Ib), but the test in americanus is much lower, not conical as in mer- 

 rilli. Twitchell described A. merrilli from the Ocala limestone of 

 Florida, and this formation was then considered as Oligocene. Accord- 

 ing to latest authority, however (see p. 110), the Ocala limestone is 

 considered as Eocene. 



Tertiary, doubtless Eocene, Jamaica. A plaster cast of the type (orig. 

 No. Y. 5), L. Agassiz collection, subscription of 1859, Mus. Comp. 

 Zool. No. 724. 



Family NUCLEOLITID^ Gregory, 1900. 



The family name Nucleolitidae is used to replace the old name 

 Cassidulidae, which had to be abandoned, since Cassidulus is pre- 

 occupied, all as set forth by H. L. Clark, 1917, Mem. Mus. Comp. 

 Zool., vol. 46, No. 2, p. 103. 



Genus PARAPYGUS Pomel, 1883. 



Type species. Botriopygus toucasanus d'Orbigny, 1855, Paleon- 

 tologie Francaise, vol. 6, Echini, p. 340, plate 931. 



The name Parapygus must replace Echinanthus as used by Desor, 

 Duncan, Cotteau, and others. For full account of this change, see 

 H. L. Clark, 1911, Ann. Mag. Nat. Hist., ser. 8, vol. 7, p. 594. 



Key to the West Indian Fossil Species of Parapygus. 



Periproct marginal; test about half as high as long; petals tend to close P. antillarum 



Periproct supramarginal; height of test over 60 per cent of length; petals not tending 



to close P. parallelus 



Parapygus antillarum (Cotteau). 

 (Plate 9, Figures 6 to 9.) 



Echinanthus antillarum Cotteau, 1875, Kongl. Sven. Vet. Akad. Handl., vol. 13, No. 6, p. 26, 

 plate 4, figs. 9 to 12; 1897, Bol. Com. Mapa Geol. Espana, vol. 22, p. 52, plate 16. 

 figs. 1 to 4. Non Gregory, see p. 39. 



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

 Species of medium size, rounded anteriorly, subtruncate posteriorly; 

 upper face swollen, thick on the sides, subcarinate posteriorly; lower face 

 nearly flat, a little hollowed antero-posteriorly. Apical disk anterior to 

 the center. Ambulacral areas petaloid, slightly swollen, fairly broad, 

 contracting at their tips, the two posterior petals a little longer than the 

 others. Poriferous areas a little depressed, with unequal pores, the internal 

 rounded, the external narrow, elongated, and oblique. The poriferous 

 areas cease being petaloid at a considerable distance from the ventral 

 border; the pores become very small and disappear among the tubercles, 

 which are small, crowded, homogeneous, and everywhere very abundant. 



