NATURAL SCIENCES OF PHILADELPHIA. 259 



to be' also less like G. melo, or any of the other species known to us from this 

 horizon, we suspect it will be found to belong to an un described species, but 

 as we have not seen the summit, nor base, we are left in doubt on this point. 

 Should it prove to be new, however, we would propose for it the name G. 

 Jinibriatus. 



Locality and position. Upper beds of Burlington group, of Subcarbonif- 

 erous series, Burlington, Iowa. Mr. Wachsmuth's collection. 



ASTEROIDEA. 



ScecENASTEK Wachsmpthi, M. & W. 

 Body flattened, with a regular, distinctly pentagonal outline, the angles being 

 produced into five rather attenuated rays or arms, which are a little convex 

 above, and apparently as much as two-thirds as long as the diameter of the 

 disc, if not more. Disc concave in outline on the outer margin brtween the 

 rays, and imparting a slightly alate character to the latter, by extending a 

 little along their inner lateral margins ; like the dorsal side of the rays, com- 

 posed above of numerous small, slightly convex plates. Dorsal pores mode- 

 rately distinct between the plates. Plates of the under side of the disk about as 

 large as the dorsal plates, but flattened, scale-like, crowded, and having the in- 

 ward imbricating character of the genus very strongly marked. Ambulacra (as 

 seen in a compressed specimen) very narrow, their adambulacral plates mode- 

 rately large, oval-oblong, comparatively thin, and very strongly imbricating 

 outwards or towards the extremity of the rays. Between these two rows of 

 short, flattened spine-like scales are seen arising from the amlmlacral furrow, 

 and all inclining outwards toward the outer extremities of the rays. (Other 

 characters unknown.) 



Diameter of disc, 1-22 inch; rays apparently extending as much as 0'90 

 inch or more beyond the margins of the disc. 



This species will be readily distinguished from our S. fimbriatus, from the 

 St. Louis limestone, the only other known species of the genus, by its smaller 

 and less convex plates on the dorsal side, as well as by its much thinner, less 

 oblique and more strongly imbricating row of plates' along each side of the 

 ambulacra, and particularly by its much narrower ambulacral furrows. We 

 have not seen any traces of the row of short flattened marginal spines seen 

 around the disc of S. fimbriatus, nor have the similar little appendages seen 

 arising in a double row from the ambulacra of the species under consideration 

 been seen in S. fimbriatus, but it is probable these are generic characters that 

 exist in good specimens of both species. There may have also been similar 

 little flattened spines on other parts of the fossil, as" there are some appear- 

 ances of such little appendages projecting from the transverse sutures between 

 some of the rows of imbricating adambulacral plates. 



We take pleasure in naming this interesting species after Mr. Charles 

 Wachsmnth, of Burlington, Iowa, its discoverer, to whom science is indebted 

 for the discovery of many interesting new types of fossils. 



Locality and position. Burlington, Iowa; upper part of Burlington lime- 

 stone of Subcarboniferous series. Mr. Waclismuth's collection. 



MOLLUSC A. 

 LAMELLIBRANCHIATA. 



PTERIA (PtERINEA ?) JIORGANENSIS, M. & W. 



Shell (left valve) exclusive of the posterior wing, obliquely subovate, mode- 

 rately convex, very thin ; anterior and basal margins forming an obliquely 

 descending, semi-oval, or semi-circular curve, from the anterior ear to the 

 posterior margin, which is prominently and rather narrowly rounded ; hinge 

 line somewhat less than the length of the shell, and ranging at an angle of 

 about 45 above a line drawn from the beak to the most prominent part of the 

 I860.] 



