ABATUS CAVERNOSAS. 211 



and the narrow ambulacra! areas of the actinal side (PI. XXXV b , fig. 2) 

 as contrasted to the broad ambulacral areas of P. Umicola from the Gulf 

 of Mexico (PI. III. fig. 4). 1 



The Mexican species is far more closely allied to the Panamic species 

 than to the Schizasterdike specimens collected by the " Challenger." The 

 abactinal system of the latter resembles that of Schizaster, while that of 

 P. Umicola and P. tenuis are Hemiasterdike, though that of P. Umicola has 

 only two genital pores. 



Station 3381, off Gale ra Point, 1772 fathoms. Lat. 4° 56' N. ; Long. 

 SO 52' 30" W. Bottom temperature, 35.8. Gn. m. 



Station 3398, off Galera Point, 1573 fathoms. Lat, 1° 7' N. ; Long. 

 80° 21' W. Bottom temperature, 3G ". Gn. ooze. 



Station 3399, off Galera Point, 1740 fathoms. Lat. 1° 7' N. ; Long. 

 81° 4' W. Bottom temperature, 36°. Gn. ooze. 



Bathymetrical range, 1573-1772 fathoms. Temperature range, SG'-SS .8. 



Abatus Trosch. 

 Abatus cavernosus Trosch. 



Tripylus cavernosus, Phil. Wieg. Arch. 1845, XI, p. 345. 

 Abatus cavernosus, Trosch. Wieg. Arch. 1851, XVII, p. 72. 



Plate 99. 



The Echiniddike type of young Spatangoids has been known since 

 1848 from Midler's figures. Subsequently I figured a number of post- 

 embryonic stages of young Spatangoids in the Revision of the Echini 

 (1874), the "Challenger," and "Blake" Echini. In 1883 Loven carefully 

 described and figured the young of Abatus cavernosus and of Echinocar- 

 dium, 2 while we owe to Fewkes and Theel more recent figures of very early 

 Echinid stages of Echinarachnius and Echinocyamus. In Loven's figures 

 of a young Echinocardium 3 of 1.7 mm. in length the coronal plates of 

 the young Spatangoid are drawn and the fascioles are indicated. In his 

 figures of a young Abatus of 2.3 mm. the plates near the actinostome are 

 figured, 4 as well as those of the abactinal system and part of those of the 

 ambulacral system. The interambulacral plates are not shown. 



i Bull. M. C. Z. 1878, No. 9, Vol. V, p. 193, PI. III. 

 2 Pourtalesia, p. 24, Pis. XIV, XV. 

 8 Pourtalesia, PI. XV, figs 172, 173. 

 4 Pourtalesia, PI. XIV, figs. 1 GO, 167. 



