208 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
second. At the anal side, which is somewhat wider, the first anal plate 
rests upon the basals, and supports three small plates in the next range, 
which are succeeded by three plates, and others above. Ventral disk asym- 
metrical, strongly bulging at the posterior side, and supporting a large 
central tube. Orals large, excentric. 
Column pentangular; axial canal small. 
Distribution. — Niagara group of America. 
Remarks. —We only recognize Roemer’s typical species. Hall’s Lamp- 
terocrinus inflatus (Balanocrinus sculptus Troost MS.) has never been described, 
and the figure* was made from a natural cast, of which the anal side is 
not seen. Lampterocrinus parvus + was also described from very imperfect 
material. 
Lampterocrinus, by its asymmetry, and the position of its anal tube, is 
very closely allied to Siphonocrinus ; but it is readily distinguished by its arm 
structure. 
Lampterocrinus tennesseensis Rormer. 
Plate XIII. Figs. 10a, b, ¢, d. 
1860. Roemer; Silur. Fauna West. Tenn., p. 37, Plate 4, Figs. la, d. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 201. 
Syn. Bulanocrinus sculptus Troost (Catalogue name). 
Calyx elongate, more than once and a half as high as wide, decidedly 
asymmetrical. Dorsal cup higher than wide, spreading abruptly to the 
middle of the radials, where it attains almost its full width; cross-section 
pentangular. Plates convex, their surface ornamented with conspicuous 
radiating ridges, passing from the centre of one plate to the centre of an- 
other — there being one ridge for each side of the plates — dividing the 
surface into well marked, deeply impressed areas. The ridges are angular, 
knife-like, their edges more or less serrated; those from the infrabasals to 
the basals, and thence to the radials, and between radials and costals, and 
to the first interbrachials, are more prominent than those of the higher in- 
terbrachials, but the centre of the latter is raised into a small, sharp node. 
Infrabasals five, completely anchylosed, forming a small cup; the suture 
lines obliterated by extraordinary secretion of calcareous matter, and raised 
into sharp ridges, passing out from the angles of the column to the lower 
* 28th Rep. N. York State Museum Nat. Hist., Plate 10, Fig. 6. 
+ 11th Rep. of Geo). and Nat. Hist. State of Indiana, Plate 15, Vig. 6. 
