13i PALEONTOLOGY OF NEW-YORK. 



Genus ProTASTER ( Forbes). 



Memoirs of the Geological Survey of Great Britain, Decade I. 



" Body circular, covered with squamiform plates : genital openings in 



" the angles of junction of the arms beneath. 



" Arms simple, formed of alternating ossicula." 



A large specimen of a similar fossil, preserved in the collections of the New- York 

 Lyceum, was designated by the late Dr. Dekay as Euryale annulatum; but I am 

 unable to find any description of it at this time. 



Protastcr forbesi ( n. s.). 



Plate VII A. Fia. 8 - 10. 



Body circular, small, composed of squamiform plates. 



Arms five, large, subequidistant, composed of a single series of joints with 



a groove along the centre of the lower side, bearing jointed tentacles 



on the outer angles of the lower margins. 



The under surface of the disc and arms only is seen in the specimen : the scale- 

 like plates are imbricated, and have granulate surfaces. The mouth is central. The 

 buccal apparatus is composed of ten parts arranged in pairs; one-half of each pair 

 springing from the base of each arm at their contiguous sides, and converging so as 

 to form a falcate-lanceolate toothlike process from the Sinuosities of the arms, and 

 projecting deeply into the cavity of the mouth. These buccal processes are evidently 

 articulated to the lateral margins of the first joints of the arms, like the succeeding 

 tentacles, and differ little in appearance from those organs. The arm-plates are sub- 

 quadrate, with concave bases and convex or pointed anterior margins, with a groove 

 along the lower side, and connected together by a small cylindrical canal. The 

 brachial plates, as seen from the lower side, are deei:)ly indented at their base, and 

 pointed above; so that when the arm was contracted, the plates closely interlocked, 

 from the insertion of the pointed extremities into the hollow bases of the succeeding 

 plate. Only four or five of the brachial ossicula of each arm are imbedded in the 

 body; but from their comparatively large size, they have doubtless extended much 

 beyond the disc. The outer lateral margins are indented near the extremities for the 

 insertion of the tentacles, which are composed of two or more joints thickened at 

 the articulating extremities. 



Fig. 8. The fossil, natural size. 



Fig. 9. Enlargement of the body and arms, with a restoration of the latter in outline 

 beyond the limits of the body. 



Fig. 10. Enlargement of portions of an arm and tentacles, as seen from the lower side. 



