48 FOSSIL ECHINI OF THE WEST INDIES. 



the test dorsally; ventrally they are similar, but more closely associated. 

 There are 4 genital pores, the pore being absent in area 5, as is typical in 

 the genus. Several madreporic pores exist. 



There are 2 specimens of this new species. The larger measures 

 3 mm. in height, 18 mm. in length, and 17 mm. in width. The fact that 

 there are only 4 genital pores indicates that this species should be 

 referred to the genus Peronella. 



This species is remarkable in the large primary tubercles which occur 

 on the dorsal side. The only clypeastroid apparently to which it can 

 be compared is the Recent Clypeaster lampas H. L. Clark (C. latissimus 

 A. Agassiz, Blake Echini, plate 15c), in which species there are a number 

 of large tubercles on the ventral side ; but they are not sunken in pits 

 and are quite numerous instead of very limited in number. A better 

 comparison structurally of the peculiar large tubercles in Peronella 

 mirabilis is to compare them with similar tubercles seen in the spatan- 

 goids Lovenia and the Recent Maretia tuberculata A. Agassiz and Clark 

 (1917, Mem. Mus. Comp. Zool., vol. 46, No. 2, plate 160, figs. 5 to 7). 

 In this comparison with spatangoids the similar character is a pure case 

 of parallelism. 



The second specimen, which is somewhat smaller and less perfect 

 than the holotype, is instructive in that it shows a similar distribution 

 of the large primary tubercles, 2 in interambulacrum 4 and 1 in inter- 

 ambulacrum 3. They also doubtless existed similarly in interambulacra 

 1 and 2, but these areas are worn away. This species was associated in 

 the same lot with Echinolampas ovumserpentis, as collected by J. A. 

 Bullbrook. 



Eocene, San Fernando formation, Vitabella Road, Mount Moriah, 

 San Fernando, Trinidad, J. A. Bullbrook collector; 2 specimens, U. S. 

 Geol. Sur. station 8878; the holotype, U. S. Nat. Mus. No. 328247; 

 and a paratype, U. S. Nat. Mus. No. 328248. 



Family SCUTELLID^E Agassiz, 1841. 

 Genus ECHINARACHNIUS Gray, 1825. 



Type species. Scutella parma Lamarck, 1816, Anim. sans Vert., 

 vol. 3, p. 11 



Echinarachnius sebastiani, new species. 

 (Plate 7, Figures 5, 6; Text-figure 4.) 



The following is a description of this species : 



Test very thin, wider than long, flat on the lower side, arched on the 

 upper side, with very thin margin. Apical disk central. Petals wide, 

 rounded and open at the distal tips, being wider open in the large specimen 

 than in the two small ones, which I take to be immature. Surface of the 

 test closely set with small tubercles. The details of the apical disk can not 

 be made out, but it is central in position. The periproct is on the posterior 

 margin in a small reentrant notch. The peristome is quite hidden by the 



