SPATANGIDAE. 501 



SPATANGIDAE. 



Family Spatangidae Agass., 1836 * Prod. Mon. Rad. (emend.) 



In this family the actinal part of the test is occupied by a plastron, the 

 sides of which are -well defined by bare ambulacral avenues. The posterior 

 ambulacra towards the posterior extremity are frequently divided by a 

 fasciole, running in such a way as to separate the two poriferous zones and 

 form a limited area (subanal plastron) or plastron, which may or may not 

 be closed, and is more or less distinct. Other plastrons are formed by the 

 fascioles consisting of a crowded pavement of miliary tubercles carrying 

 miliary spines, running either within the petals (internal), or round the petals 

 (peripetalous), from which sometimes branches are sent off towards the anal 

 extremity (lateral). When the sub-anal fasciole sends a branch round the 

 anal system it forms the anal fasciole ; the lateral becomes the anal fasciole 

 when it runs continuously below the anal system, round the posterior ex- 

 tremity of the test. The combination of these fascioles together with the 

 shape of the test and of the petals has been made the most important 

 element in the subdivisions into subfamilies of the Spatangidae. 



ANANCHYTIDAE. 



Subfamily Ananchytidae Alb. Gras, 1848, Ech. foss. Isere. 

 (See Part II. p. 344.) 



POURTALESIA. 



Pourtalesia A. Ac, 1869, Bull. M. C. Z., I. 

 (See Part II. p. 344.) 



Pourtalesia miranda 



! Pourtalesia miraiida A. Ag., 1869, Bull. II. C. Z, I. p. 272. 

 (See Part II. p. 345.) 



PI XVIII. 



Straits of Florida ; Shetland Channel. 



* Should read Agass., 1836, on p. 344, not Agass., 1841. 



