////; STELLEROIDEA 



257 



pentagonal. Genera Cheiroptaster, Stiirtz ; ],i>i-i<>l<i.-<t<-r, Stiirtz ; (1) llho- 

 palocoma, Salter. SUB-FAMILY 2. PTERASTERINAE, with a well-developed 

 supra-dorsal membrane, opposite ambulacral plates, and actino-lateral 

 spines. Form pentagonal. Genera Benthaster, Slad. ; Call/piaster, Slad. ; 

 Cryptatter, Per. ; Flexaster, Per. ; Hymenaster, Wyv. Thorns. (Fig. XII.) ; 

 Marsipaster, Slad. ; Myxaster, Per. ; Stemster, Mull. & Tr. ; Eetaster, Per. 

 SUB-FAMILY 3. PYTHONASTERINAE, with stellate form, opposite ambulacral 

 ossicles, and rudimentary marsupium formed by five triangular fan-like 

 valves ; no segmental apertures or actino-lateral spines. Genus Mayr- 

 nster, Per. ; 1'ythonastcr, Slad. 



FAMILY 9. PALASTERISCIDAE. Cryptozonia with the ambulacral 

 ossicles alternate for at least part of the arms. The madreporite is 



FIG. XII. 

 IhinK'iK.tftrr i^Uiirlihis (after Wyv. Thomson). 



large and ventral in position. Actino-lateral spines are present. The 

 dorsal integument is granular. The form is stellate with small inter- 

 brachial areas. Genera Pfdiixti'rixcn.s, Stiirtz ; Echinasterella, Stxirtz. 

 This family is remarkable for the abnormal position of the madreporite, 

 which, unlike that of recent Asteroids, is ventral in position. This char- 

 acter is possibly due to the development of a granular integument over 

 the whole of the abactinal surface. Large spine-like paxillae occur, and 

 it is quite possible that the granular integument was the roof of a large 

 marsupium. There can be no question as to the position of the madre- 

 porite, for the actinal and abactinal surfaces of the same specimen are 

 shown in examples in the British Museum. 



FAMILY 10. ECHINASTERIDAE. Cryptozonia with a reticulate abac- 

 tinal skeleton of small imbricating plates. Ambulacral ossicles opposite ; 

 the pores biserial ; oral armament adambulacral. Interbrachial septa 



17 



