REPOBT ON THE ECHINOIDEA. 169 



miliary tubercles arranged in lines between the primary tubercles. This structure is very 

 marked in young specimens, and plainly shows the manner in which the fascicles pass from 

 miliary tubercles into the regular fascioles. 



This species diflers from the West Indian species in having a more flattened test, and 

 better defined petaloid ambulacra ; in having a subanal and a peripetalous fasciole ; and 

 in having far larger and longer primary spines ditfering greatly in size on difi'erent 

 parts of the test ; while in Paleopneustes cristata the spines covering the abactinal 

 part of the test are remarkably uniform, with the exception of the tuft of primary 

 spines near the apex. 



Seen from above the test is elliptical ; the odd ambulacrum is slightly sunken at the 

 ambitus, the median odd interambulacral space also re-entering immediately above the anal 

 system (PI. XXV. fig. 1). Seen in profile (PL XXV. fig. 3) the apical system and apex 

 coincide ; the apical system is central, and from this the test arches regularly towards the 

 anterior and posterior extremities, sloping more rapidly towards the posterior extremity, 

 and being more gibbous towards the anterior extremity. The posterior extremity is 

 truncated from the anal system placed above the actinal surface (PI. XXV. figs. 3, 5). 

 The actinal surface is flat, with the exception of the slightly sunken anterior ambulacrum, 

 and the slight keel formed by the actinal plastron, which projects but little beyond the 

 general level of the actinal surface (PL XXV. figs. 2, 4). The actinostome is excentric, 

 placed towards the anterior extremity (PL XXV. fig. 2) about one-third of the length of the 

 test. It is elongated, transverse, with a prominent actinal lip (PL XXV. fig. 7) with broad 

 ambulacral plates, separated at the edge of the actinostome by exceedingly narrow inter- 

 ambulacral plates ; with the exception of the broad plate forming the lip, the actinal 

 membrane is strengthened by two irregularly concentric rows of numerous triangular 

 plates ; the actinal opening is close to the posterior edge of the actinostome. 



The anal system is circular, covered by numerous plates forming four or five irregular 

 concentric rows round the anal opening ; the outer row of plates are elongated, the others 

 are irregular in shape (PL XXV. fig. 6). The extremity of the indistinct rounded actinal 

 keel is surrounded by a broad well-marked fasciole. The peripetalous fasciole extends 

 from the end of the posterior lateral petal, sloping towards the end of the anterior pair 

 where it becomes indistinct ; its course is also very poorly defined across the odd interam- 

 bulacral area. This fasciole is quite narrow and often even the part running between the 

 lateral ambulacra, figured on Plate XXV. fig. 3, is quite indistinct and broken. On 

 the actinal side (PL XXV. fig. 2) the tuberculation is limited to the edge of the test 

 adjoining the ambitus mainly in the interambulacral spaces ; the tubercles are c|uite 

 uniform in size, leaving broad, bare ambulacral avenues, slightly tuberculated at the 

 ambitus; round the actinostome (PL XXV. fig. 7) there are only miliary or small 

 secondary tubercles (PL XXV. fig. 2). On the abactinal surface the tuberculation is very 

 irregular ; each coronal plate carries in the interaml)ulacral area a numljcr of prunary 



ZOOL. CHALL. EXP. — PART. IX. — 1881) I 22 



