14'2 



T 1(11 traction > 



Asteropsis of Mi'illei' and Ti-oschel and Dennasterias of Perrier (1875). 

 Unfortunately, I have not access to Perrier's original paper, but I rely on 

 81aden's diagnosis of the two genera (" Challenger " Report, p. 355). One 

 difference (I gather both from 8hiden and from Bronn's " Thierreichs ") 

 lies in the presence of a distinct " composite reticulated meshwork " formed 

 by the abactinal plates in Derniastcrias, while the skeleton of Asteropsis 

 consists of " irregular substellate plates not forming such a network." From 

 the account of the largest specimens given below it will be seen that in the 

 adult of this species such a " composite reticulated meshwork " does exist, 

 but in other features the genera are quite distinct. 



The material at ni}' disposal consists of — (a) Large specimens, both 

 dried and in alcohol : (6) Farquhar's type, which is of intermediate size : 

 (c) small ones, dried. 



(a.) The dried specimens are somewhat compressed and distorted, but 

 the plates are pretty distinctly seen. Avhile in those preserved in alcohol the 



skeleton is entirely con- 

 cealed l)y the tough skin, 

 which is wrinkled on the 

 abactinal surface, and 

 especially near the tips 

 of the rays, but is smooth 

 on the actinal surface. 

 This skin encloses and 

 connects the adambu- 

 lacral spines so as to 

 form 2 thick membranes 

 on each side of the 

 groove, one lying in the 

 furrow, the other along 

 its margin. 



Dimensions. — The 



dried specimens measure 



R 75. r 34 ; R 70, r 31. 



The alcoholic specimen 



gives R 56. r 24. Thus 



;• : R = 1 : 2-20 to 2-33. 



The form is stellate. 



w i t h r o u n d e d i n t e r- 



h r a c h i a 1 angles . The 



rays are broad at the 



base (3 mm.), tapering gradually to a rounded apex. At about midway 



along the ray is 15 mm. across. The figure given by Farquhar represents 



well the general appearance of a pi'eserved specimen. 



The madreporite is prominent and round, situated rather nearer to 

 centre than to the margin (as 12 is to 20). The anus is surrounded by a 

 circle of short cylindrical spines, about 10 in number, which close over it. 



The abactinal skeleton forms an open meshwork, with large papular 

 areas, separated by short rows of nai-roA\- flattened ossicles about half as 

 wide as they ai'e long, which radiate from a series of 5- or 6-lobed plates 

 at the nodes of the network. Ther(> is a r)-lobed central plate with the 

 anus close to one side ; from it radiate outwards short rods, forming a 

 series of wide meshes around it. At the intcuvradial margin of this circle 

 are 5 irregularly stellate plates, one of which bears the madreporite. 



Fig. 1. — A'Sterop«i-'< hn/x'n'ali.s. 



The central portion of the ilise (x 2). ce., central ; <■ 

 centro-radial : /.;■.. interradial ; rl. primary radial 



