. Annual report of the regents of the university of the state of New York on the condition of the State Cabinet of Natural History and the historical and antiquarian collection annexed thereto. Science. 166 [Senate Cyrtia hamiltonensis ()- Shell more or less obliquely triangular pyramidal; hinge equal- ling the greatest breadth, and obtusely angular at the extremi- ties : dorsal valve depressed, nearly flat; beak scarcely elevated above the hinge-line ; mesial fold small, bounded on each side by deeper and wider grooves than those between the plications, with sometimes a f
. Annual report of the regents of the university of the state of New York on the condition of the State Cabinet of Natural History and the historical and antiquarian collection annexed thereto. Science. 166 [Senate Cyrtia hamiltonensis ()- Shell more or less obliquely triangular pyramidal; hinge equal- ling the greatest breadth, and obtusely angular at the extremi- ties : dorsal valve depressed, nearly flat; beak scarcely elevated above the hinge-line ; mesial fold small, bounded on each side by deeper and wider grooves than those between the plications, with sometimes a faint narrow longitudinal depresssion in the middle : ventral valve very convex, most prominent near the beak, which is very variable in elevation, and either straight or a little arched from the hinge, sometimes twisted on one side ; sinus distinct, rounded or angular ; area variable, triangular, generally high, often wider than high, arcuate or plane, finely striate in both ways, the vertical striae scarcely visible ; foramen very narrow, usually perforate above by an oval or narrow ovate aperture, and has at its base a small transverse arcuate slit. Surface ornamented by six to eight simple rounded plications on each side of the mesial fold and sinus, and marked by very fine concentric lines of growth. Under a good lens minute gra- nules may be seen on all parts of the exterior except the area and deltidium : interior minutely punctate. This species may be distinguished from the C. dalmani of the Lower Helderberg limestones, by never showing the strongly imbricating lamellae of growth which mark that species. It is, however, more nearly related to Cyrtia [Spirifer) heteroclitus, VoN BuCH ; and until we know the limits of the variation in that species, it will be very difficult to point out cha- ^cters by which our shell can be distinguished from it. Ideological position and locality. In the shales of the Hamilton group: \s of Seneca lake, Moscow, York, Darien, and Eighteen-mi
Size: 1907px × 1311px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, booksubjectscience, bookyear1853
