548 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



closely resembles Phi/setocrinus, but that, having no anal plate in the first 

 interbrachial row, is an Actinocrinoid. 



Gennseocrinus kentuckiensis (Shumaed). 

 Plate XXXIV. Figs. 11, 12, 13. 



1866. Adinocriiias kentuckiensis — Shumaed; Trans. Acad. Sci. St. Louis, Vol. II., p. 3i5. 

 1881. Gennceocrinus keiitackioisis — W. and Sp. ; Rerision Palaeocr., Part II., p. 161. 



Syn. Actinocrinits coniit/erus Lyon and Casseday, 1859 (not BLiLi, 1S58) ; Amer. Journ. Sci. 

 (u. series), Vol. XXVIII., p. 238. 

 - Syn. Actinocrinits mjssa Hall, 1S62; IStli Rep. N. Y. State Cub. Albany, p. 129. 



Of medium size. Calyx wider than high, decidedly lobed at the arm 

 regions, and the arms given off in clusters. Dorsal cup semiglobose ; the 

 surface covered with well-defined striae proceeding from the centre of the 

 plates to their margins. There is a ridge to each face of the fjlates, and 

 another to each angle, which meet with similar ridges from adjoining plates, 

 and form with them all sorts of triangles. The ridges following the rays 

 increase in prominence as they approach the distichals, and attain at the 

 arm bases almost the width of the arms. 



Basals very short, slightly projecting laterally, forming a thin trilobate 

 rim, which is flat at the bottom. Radials and costals as long as wide, de- 

 creasing rapidly in size upward ; the second costals less than half the size of 

 the radials. Distichals 2 X 10, comparatively small, wider than long ; the 

 second ones axillary, supporting 2X4 palmars, of which the two of the 

 outer sides are followed by one arm, the two inner ones by two arms, the first 

 plate taking part in the calyx. There are eight arms to each ray, in close 

 contact ; while those of different rays are far apart. Whether there is any 

 branching in the free arms is not known, Interbrachials : 1, 2, 4 (some- 

 times 1, 3, 4) ; succeeded by one or two rows of smaller pieces, of which the 

 upper interlock with the inter ambulacra! plates. The first anal piece sup- 

 ports three large plates in the first row, five in the second, and five or more 

 in the third. Interdistichals three in two rows. Ventral disk depressed- 

 convex ; the interambulacral plates together with the interbrachials form 

 wide and deep recesses around the calyx, while the radial portions project 

 conspicuously upward and outward. All plates of the tegmen of nearly uni- 

 form size, and each one covered with a small central tubercle. Orals com- 

 paratively small, even the posterior one, which is central, being but little 

 larger than the other plates. Ambulacra covered by two rows of alternating 



