EOHINODERMATA. 
325 
ellipticum, elongatum, rostratum, marginale, stellatum, Ag. ; tonga- 
nense^ Quoy and Gain.; Lesueuri, Val. ; orbiculare, Ag., L., Gm. ; 
Peronii, Ag. (Scutella orbicularis, Lam.) Of the genus Echinocyamus, 
only two living species are described; E. pusillus, Flem., and angu- 
losus, Leske. Moulinia is the thirteenth and last genus, embracing 
the single species, M. cassidulina. 
After the third livraison of Agassiz’s Monographies, which treated 
only of antediluvian Echinidce (1842), a very comprehensive monograph 
appeared by Valentin, on the anatomy of the genus Echinus (Monogra- 
phies d’Echinodermes 4 e. livraison, contenant I’Anatomie du genre 
Echinus, par G. Valentin, 1842). He distinguishes in the shell of the 
Echinus three kinds of calcareous plates ; the largest form the principal 
mass of the shell, the two others comprehend the smaller buccal and 
anal plates. The anal plates are held together by a contractile mem- 
brane. All the plates, with the exception of the buccal, bear spines, 
which are fixed by theif articulating heads in a muscular layer. The 
suckers of the ambulacra are extraordinarily contractile, and can be pro- 
jected, by the living Echinus, far beyond the longest spines, in order to 
touch with them or to move forwards ; each sucker is furnished at its 
free end with an acetabulum. Besides these long pedicelled acetabula, 
the Echini possess other stalked appendages, which are very abundant 
round the mouth, and were formerly supposed to be parasitic animals 
and young brood of the Echinus. Valentin divides them into three 
kinds according to their shapes, and calls them pedicellaires gemmi- 
formes, tridactyles, and ophiocephales. He has also very exactly de- 
scribed the Laterni of Aristotle ; and the vascular system has been sub- 
jected to a careful investigation. 
As supplementary to this excellent monograph, the works which ap- 
peared almost simultaneously on Echinus, by Erdl, Krohn, and Kblliker, 
are to be mentioned. 
Erdl’s researches have been particularly directed to the spines, ace- 
tabula, and pedicelli of the mouth, as well as to the external branchiae of 
the Echinus saxatilis (Arch. 1842, i. p. 48). Krohn’s communications 
are confined to the description of the nervous system of the Echinus and 
Spatangus (Miill. Arch. 1841, p. 2, and Ann. d. Sc. Nat. t. 16, p. 288). 
The separate sexual organs have been recognised by Kolliker in 
Echinus saxatilis (Beitrage zur Kenntniss der Geschlechtsverhaltnisse 
und der Samenfliissigkeit wirbelloser Thiere, Berlin, 1841, p. 39). 
Agreeably to what had formerly been pointed out on these parts in the 
Echini by Peters (Mull. Arch. 1840, p. 143, Fror. N. Notiz. No. 275, 
p. 168, and Ann. d. Sc. Nat. t. 13, 1840, p. 196), Milne Edwards and 
Lallemand (Ann. d. Sc. Nat. t. 13, 1840, p. 376, and Fror. N. Notiz. 
No. 300, p. 218) ; and by Valentin (Repertor. f. Anat. und Physiol. 
1840, p. 301) in Spatangus. 
369 2 A 
