292 HEMIPEDINA CUBENSIS. 



in lateral arcs of three pairs (PL III. f. 4). The general outline of the test 

 is that of Phymosoma, there are only two rows of tubercles extending from 

 pole to pole ; the flatness of the abactinal part of the test (PI. Ill /'. 5), 

 and the great development of the abactinal system, remind us of some forms 

 of Bemipedina, as, for instance, Hemipedina G-uerangeri Cott. ct Trig., fig- 

 ured in PL XXII. f. 5, Echin. de Sarthe. The actinal opening is small, with 

 sharp cuts for the passage of long, narrow gills (PL III. f. ,?). The spines 

 are long, moderately stout, as long as the diameter of the test, longitudi- 

 nally striated, resembling the spines of some species of Hemipedina figured 

 by Wright. The pores are arranged in vertical connected arcs, of from 

 three to four pairs. There are two rows of perforate primary tubercles in 

 the ambulacra] area, decreasing rapidly in size towards apex, and placed 

 close together (PL III. f. 3). They are considerably smaller than those of 

 the interambulacral area. There are one or two small imperforate tubercles 

 at the base of the larger ones. The poriferous zone is broad and well 

 defined, spreading slightly at actinostorae (PL III. f. :.')■ 



The perforate interambulacral tubercles are arranged in two primary rows, 

 separated from the poriferous zone by a row of small imperforate tubercles 

 (PI. III. f. ./). with two or three similar irregular rows between the larger 

 tubercles in the median interambulacral zone. The pedicellaria 1 of test, near 

 the abactinal pole, have very large, broad, open arcs (PL III. f. i;). when full 

 grown, resembling those of Echinus proper; the young pedicellarise (PL III. 

 f. ?) are more compact. The plates of the abactinal system are large (PL III. 

 /. i), with straight sides; the genital are heptagonal, carrying five to six 

 small tubercles, and as many still smaller ones. The ocular plates are pen- 

 tagonal, with a large ocular pore surrounded by an arc of small tubercles. 

 The plates covering the large anal system are very numerous and minute. 

 The anus is situated in the very centre of the anal system. The teeth re- 

 semble those of Arbacia. The buccal membrane is strengthened round the 

 mouth, close to the teeth, by ten large plates (PL III. f. ;.'), (perforated for 

 buccal tentacles,) occupying nearly the whole membrane, with eight to ten 

 very much smaller ones between the large plates and test. The color of the 

 large spines, in alcohol, is of a dull yellowish-green, while the smaller spines, 

 as well as test and abactinal plates, have a more yellowish tint. 



Diameter. Height. Abactinal System. 



11.2 4.8 6.4 



From 138 to 270 fathoms. 



