300 
PALAEONTOLOGY OF NEW YORK. 
There are at least three well known species which are clearly referable to 
this proposed genus: Leptcma subquadrata, Hall,* * * § from Perry county, Tennessee, 
referred to the age of the Lower Helderberg group; Leptcena tenuicincta, McCoy, 
elaborately described by Mr. Davidson,! from the Upper Llandeilo and the 
Caradoc series; Pledambomtes ovata and P. oblonga, Pander, which are united 
by de Verneuil! under the term Leptcma oblonga , from the Lower Silurian 
beds in the vicinity of St. Petersburg. Davidson includes in L. tenuicincta the 
Leptcena cenigma of de Verneuil, § from the Lower Silurian beds of the Island of 
Gotland, a shell much less elongated than the typical L. tenuicincta, and whose 
interior has not been described. 
Genus LEPTiENISCA, Beecher. 1890. 
PLATE XV, FIGS. 30, 31; and PLATE XVA, FIGS. 19-30. 
1859. Leptcena, Hall. Palaeontology of N. Y., vol. iii, p. 197, pi. xviii, fig. 2, 
1883. Leptcena ? (sub-genus ?), Hall. Rept. N. Y. State Geologist for 1882; Expl. pi. xv (46), figs. 30,31. 
1890. Leptcenisca, Beecher. American Journal of Science, vol. xl, p. 238, pi. ix, figs. 1-9. 
Diagnosis. “Shell concavo-convex, attached to foreign objects by calcareous 
cementation of the ventral beak. Valves articulated by the teeth and sockets. 
Dorsal or socket valve concave; interior with a broad, more or less defined, 
spiral impression on each side of the median line, making a single volution. 
Adductor impressions small. Cardinal line [area] narrow, bearing in the center 
two prominent, bilobed, cardinal - processes, separated to admit the vertical 
septum in the opposite beak. Ventral valve convex, area elongate-triangular, 
fissure covered with a pedicle-sheath. Cardinal muscular scar supported on, or 
limited by a vertical septum, on each side of which, in the anterior half, is a 
small adductor scar. Shell-structure punctate. 
“ Type, Leptcena concava, Hall.”* Lower Helderberg group. 
This interesting genus includes a few species of attached shells having the 
general form and contour of Plectambonites, but with a peculiar combination 
* This species is first mentioned and illustrated in the Report of the N. Y. State Geologist for 1882, 
explanation of plate xv (46), figs. 32, 33. 1883. 
t British Silurian Brachiopoda, pp. 326-328, pi. xlvii, figs. 7-18. 
t Geologie de la Russie, etc., p. 228, pi. xv, fig. 2. 
§ Bulletin de la Society Geologique de France, 2e Ser., vol. v, p.,340, pi. iv, fig. 6. 1848. 
|| Beecher. “ On Lepthsnisca, a newjgenus of Brachiopod from the Lower Helderberg group ” (op. cit.) 
