62 BULLETIN OF THE LABORATORIES 



Length of right valve from beak to postero-ventral convexity 17 

 mm; hinge posterior to beak 13 mm, height 13 mm; greatest diame- 

 ter (from ear to postero-ventral angle) 19 mm. This species is inter- 

 mediate in characters between Z. ortoni and L. rafinesquii. Like the 

 latter the wing is acute and the posterior margin excavated, like the 

 former the body is very oblique. Top of freestone, Granville. 



L. halli may be compared with Leptodesma clitus, H., but is not 

 so produced behind and rather less oblique, it is also less oblique than 

 L. lepidum. Perhaps the closest resemblance is with Leptodesma ly- 

 sander, but the wing is not so extended. 



Leiopteria, sp. 



A very small species of this genus was secured from the lower 

 shaly layers at Moot's run, probably below the horizon of L. ortoni, 

 but which more nearly resembles L. halli in the acute wing and exca- 

 vated posterior margin. The species is known only from a single 

 right valve with a short, lobate, obtuse ear. The body is more oblique 

 and narrower than in either of the preceeding species. 



Prof. Hall states that only two of the fifty-seven species of Lep- 

 todesma occur below the horizon of the Chemung, Leiopteria, on the 

 other hand, reaching its greatest ■ development in the Hamilton. 

 Pterinopecten has many species below the Ghemung, while Grenipec- 

 ten and Pteronites are unknown below. Glyptodesma is not known 

 above the Hamilton. 



Leiopteria sp ? 

 (Plate HI, Fig. 6 ) 



A fine large species is indicated by a fragment not exhibiting the 

 structure of the hinge and ears. The body is very flat, but the ante- 

 rior ear is well-defined by a strong ridge, the umbonal slopes make an 

 angle with each other of about 60°. The posterior lower angle is 

 produced. Surface marked by obscure folds and striae. Length 

 along post-umbonal ridge 27 mm, along anterior umbonal ridge 17 

 mm. The considerable obliquity and flatness of the body are the 

 obvious characters which are noted especially because the shell is 

 found in a higher horizon than those previously mentioned. 



