ECHINODERMATA. 147 



dichotomously and afterwards into many branches, in Astrophyton 

 LINCK. To the last division belongs : 



Sp. Euryale verrucosum LAM., Asterias Caput Medusae L. (in part) RUMPHIUS, 

 Amb. Rariteitlcamer Tab. xvi. Cuv. R. Ani., edit. Mus., Zooph. PL 5, from 

 the Indian Sea ; a very similar species is found in the North Seas, and 

 distinguished by MUELLER and TROSCHELL as Astrophyton Linckii ; LINCK 

 de Stell. mar. Tab. 29, fig. 48. These Medusa-heads belong to the most 

 singular and beautiful forms of radiate animals. Vid. FORBES Br. Star- 



8, pp. 6770. 



Ophiura LAM. Arms five, undivided, serving for creeping, scu- 

 tate, articulate. Disc plane, with two or four genital fissures in 

 each interbrachial area on the ventral side. 



The name Ophiura, from acpis, serpent, and ovpd, tail, denotes very 

 appropriately the form of the arms by which these Sea-stars are 

 distinguished, and which are often so long as to exceed five or six 

 times (nay in Ophiura longipeda even twenty times) the diameter 

 of the disc. 



Sub-genera : Ophiocoma AGASS., Ophiolepis, Ophiarachna, Ophia- 

 cantha, Ophiomastix, Ophiomyxa, Ophioscolex, Ophiothrix, Ophio- 

 cnemis, Ophioderma, MUELL. and TROSCH. 



Sp. Ophiura teocturata LAM., Asterias ophiura L. (in part), Ophiolepis ciliata 

 MUELL. and TROSCH., LINCK de Stell. mar. Tab. n. fig. 4, Encydop. PI. 123, 

 fig. 2, 3. FORBES British Starf. p. 22, &c. in the Mediterranean, the 

 North Sea, &c. 



Phalanx II. Asterice. Body depressed, angulate or stellate 

 the angles being produced, with tentaculiferous furrows below, ex- 

 tending as far as the point of the angles. Anus dorsal in most, 

 surrounded by a mound of calcareous papillae. 



Asteria LAM. (Most are species from the genus Asterias L.) 



The Sea-stars. The form is very various, so that in some species 

 the entire body seems to consist only of arms, ex. gr. in Ophidiaster, 

 in others only of a pentagonal disc. But the arms are never 

 sharply separate from the disc as in the Ophiurce, but are an 

 immediate continuation of it. In most of the species there are five 

 rays, however in these sometimes four or six occur as exceptions ; 

 six arms as the normal number are found in Asterias gelatinosa, in 

 Echinaster eridanella, six or seven in Asteriscus Diesingii, seven to 

 nine in the sub-genus Luidia, eight to ten, mostly nine, in Solaster 

 endeca, eleven to fourteen, generally twelve, in Solaster papposus, 

 twelve or thirteen in Asterias aster, fifteen in Asteriscus rosaceus, 



102 



