296 TWENTIETH KEPORT ON THE STATE CABINET. 



central spine. Eacli of the other plates of the areas, in the upper part of 

 the body, bears one or more small spinules ; while in the central portion 

 these become strong spines. 

 Ambulacral areas narrow, contracted towards their upper ends, composed 

 of a double series of very short curved poral plates, alternating and 

 interlocking at their adjacent margins ; each plate pierced by two small 

 pores near the outer extremity. There are from three to four of these 

 plates in the space of one-tenth of an inch, and they are slightly imbri 

 cated in a direction opposite to those of the interambulacral areas. 

 The summit of the specimen is composed of several ornamented plates, 

 arranged in the form of a pentagon ; the precise number and form of these 

 plates cannot be determined. Just within one of the angles of this penta- 

 gon, and occupying the position of the madreporic tubercle in modern 

 Echinoderms, there are impressions of what appear to have been the bases 

 of several [six?] plates, arranged in a circle, and having precisely the ap- 

 pearance of the ovarian pyramid as seen in Agelacrinus. The oral aper- 

 ture has been quite small, and centrally situated. 



This species, in its generic features, is identical with L. imhricatus^ the 

 type of the genus from the Burlington limestone ; and in its specific charac- 

 ters it is very similar. 



The imbrication of the plates is a very marked feature in two specimens 

 of this species, and their condition is such as to leave no question that the 

 imbrication is from the ventral side, and not from the apex, being the 

 reverse of the relation described in the L. imhricatus ; and it is possible 

 that from the imperfect condition of the specimen described, I may not 

 have distinguished the relations of parts. In the species under considera- 

 tion, there is a central range of vertically imbricating plates which cover 

 the lateral margins of the adjacent ranges, so that the lateral imbrication 

 passes beneath them, instead of showing an alternation along the central 

 line or suture, as in the Burlington species. 



It is scarcely necessary to comment upon the interest, in a geological 

 view, which attaches to a species of this character in rocks referred to the 

 Devonian period. 



Geological formation and localities. In the Chemung sandstones : at 

 Meadville, Pennsylvania (an impression in a specimen of the rock associated 

 with Crania leoni ) ; and in the ferruginous sandstones of Licking county, 

 Ohio. The latter was received from Prof. Carter, formerly Professor of 

 Natural History in the College at G-ranville, Ohio. 



The fossil from Meadville occurs in such position and relations that I 

 believe no one will question the geological horizon; but the sandstones of 

 Licking county, Ohio, constitute the upper part of the TVaverly sandstone 

 series of that State, and have been referred, by many geologists, to a 

 higher position than the Chemung of New-York. The occurrence of this 

 fossil, in these two localities, would certainly offer an argument of some 

 weight in favor of the parallelism of the formations. 

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