58 PALEOPNEUSTES CRISTATUS. 



tubercles in the interambulacral areas near the abactinal system, and the 

 coarser tuberculation of the odd anterior groove above the ambitus ; also in 

 having a larger number of primary plates. No part of the anal system or 

 of the actinal system was found among the fragments. 



Paleopneustes cristatus A. Ag. 



Off Havana, S. side of Cuba, Lesser Antilles. 5(5—150 fathoms. 



Most common to the leeward of the West India Island.-, between 90 and 150 fathoms. 



For list of Stations, see Bull. M. C. Z., VIII., No. 2, p. 81, 1880. 



PL XXI. 



A number of specimens of this species have been collected by the Blake, 

 which are interesting as throwing additional light on the variability of the 

 so-called lateral fasciole of this genus, and in showing tbe changes due to 

 growth. Thus far only large specimens of this genus had been described, 

 both from the Hassler and the Challenger expeditions. I have added to 

 the figures of two of the principal stages of growth given on Plate XXI. 

 Figs. 6-14, details of the actinostome (Fig. 5), of the apical system (Fig. 3), 

 of the termination of the lateral petaloid ambulacra (Fig. 1), of the edge of 

 the test near the ambitus from the abactinal side (Fig. 2), taken from a large 

 specimen of this species measuring nearly 150 mm. in length and 80 mm. in 

 height, as these details could not be very clearly seen in the photographic 

 illustrations of this species in the Memoir on the Echini of the Hassler 

 Expedition (PI. IV. Figs. 1-3, 111. Cat. M. C. Z., No. 8). 



A small specimen measuring 45 mm. in length (PI. XXI. Fig. 7) differed 

 from the specimen figured in the Hassler Echini merely in size, and in 

 having an indistinct lateral fasciole extending obliquely from the abactinal 

 end of the anal system to the edge of the test, reaching the ambitus at the 

 anterior lateral ambulacra, and extending faintly across the anterior part 

 of the test along the ambitus. See Plate XXI. Fig. 7. and Fig. 8. which 

 shows a small part of this fasciole close; to the ambitus across the anterior 

 ambulacral area. This can hardly be termed a lateral 1'asciole; it reminds 

 us of a similar fasciole in Calymne, and it is difficult to decide in these cases 

 whether this single fasciole should be called peripetalous as it passes across 

 the posterior extremity of the test above the anal system, or a lateral 

 fasciole occurring isolated from a peripetalous one; or whether it represents 

 a rudimentary stage of the peripetalous fasciole. not crossing the ambulacra 



