. 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. um, and hinge structure as in the other species. The proportions of length of rostral cavity and muscular impressionvary in different species ; and the muscular impression becomes muchstronger and deeper in the older shells, when the valve, as before remarked,becomes thickened at the sides and towards the beak. This character per-tains to the limestone specimens; while those in the Hamilton shales, asfi
. 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. um, and hinge structure as in the other species. The proportions of length of rostral cavity and muscular impressionvary in different species ; and the muscular impression becomes muchstronger and deeper in the older shells, when the valve, as before remarked,becomes thickened at the sides and towards the beak. This character per-tains to the limestone specimens; while those in the Hamilton shales, asfigs. 7 & 8, have thinner shells, and less deep and strong muscular impres-sions. I have already (Thirteenth Report on the State Cabinet, pp. 73 - 75,and illustrations on p. 93) pointed out the distinction between Athyris= Spirigera and Meristella. This difference is everywhere clear andunmistakable, in the external lamellose surface of the one, and the almostsmooth character of the other. The muscular impressions of the ventralvalve of Athyris are at once distinguishable from those of Meristella,as may be seen on comparison of figs. 35 & 36 with figs. 29 & 30.
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectscience, bookyear1853
