CLASS II ASTEROIDEA 205 
of the recent genera Ophiolepis, M. and T.; Ophiocten, Liitk. (Fig. 331); Ophio- 
glypha, and Ophiomusium, Lyman. Some of the forms described under the head 
of Geocoma, d’Orb. (such as G. socialis, Heller, from the Callovien of La Voulte ; 
or G. Libanotica, Konig, from the Cretaceous of Hakel, Lebanon), are incap- 
able of precise determination; others (such as G. carinata, Goldf., Fig. 332) 
are closely related to the recent Amphiura. 
Ophiurella elegans, Agassiz, from the Lithographic Slates of Solenhofen, is 
referred by Liitken to Ophiocoma, Agassiz. Other Jurassic and {Cretaceous 
forms which have been described under various generic names are assigned 
by the same author to Ophioglypha, Lyman. Fossil Ophiuroids which do not 
admit of critical determination are usually grouped together under the general 
term of Ophiurites. 
Class 2. ASTEROIDEA. Star-fishes.! _ 
Asterozoans whose simple and more or less flattened arms are prolongations of 
the central disk, and contain the hepatic appendages of the alimentary canal, as well 
as the generative organs. Ambulacral feet disposed in rows along deep open 
grooves on the under or actinal surface of the arms. 
Star-fishes have typically five arms (but in some cases as many as eight, 
ten, twelve, twenty, or more), which are prolongations of the central disk, 
and are not sharply marked off from the game. The integumentary skeleton 
consists of plates which are either contiguous with one another along their 
edges, or are united in a reticulate fashion, and covered with a leathery skin. 
The calcareous plates often bear movable spines or bristles, or they may be 
tuberculated or granulated. The abactinal surface usually exhibits a central 
or subcentral anus, and also a madreporite, which is situated in one (rarely 
two or more) of the interradii. The madreporite is covered with labyrinthic 
furrows, and is perforated for the admission of water into the so-called stone 
canal, whence it is conveyed into the water-vascular ring surrounding the 
mouth. The fine pores and protrusive coecal processes (papulae), which in the 
Phanerozonia are restricted to the dorsal surface, but in the Cryptozonia are 
distributed-over the whole body, serve as respiratory organs, the body fluids 
being brought into close contact with the oxygenated water. 
The mouth occupies the centre of the dorsal surface, and is pentagonal in 
contour, owing to the projection of five pairs of interradially disposed oral 
1 Literature : 
Forbes, E., British Fossil Asteridae (Mem. Geol. Survey, vol. II., Part II., and Decade III.), 1848 
and 1850. 
Salter, J. W., New Palaeozoic Star-Fishes (Ann. and Mag. Nat. Hist. XX.), 1857. 
Gray, J. E., Synopsis of the Species of Star-Fish in the British Museum, 1866. 
Simonowitsch, S., Ueber einige Asteroiden der rheinischen Granwacke (Sitzungsber. Wien. Akad. 
EY 1871. 
Sars, G. O., Researches on the Structure, ete., of the genus Brisinga. Christiana, 1875. 
Perrier, £., Revision de la Collection des Stellerides du Musenm d’Hist. Nat. de Paris (Arch. de 
Zool. Expérim. IV., V.), 1875-76. 
Agassiz, A., North American Star-Fishes (Memoirs Museum Comp. Zoology, Cambridge, V.), 1877. 
Viguier, C., Anatomie comparée du squelette des Stellerides (Arch. de Zool. Expérim. VII.), 1878. 
Sladen, W. P., Report on the Asteroidea (Scient. Results, Challenger Expedition, XXX.), 1889. 
Sladen, W. P, Monograph on the British Fossil Echinodermata ‘from the Cretaceous F ormations, 
Vol. Il. Asteroidea (Palaeontographical Society), 1890-93. 
Fraas, E., Die Asterien des weissen Jura (Palaeontographica, XXXII.), 1886. 
