106 [June, Dr. Hallowell remarked that we had recently received Ihrough Mr. Vogt, a large collection of living specimens of Siernothaerus odoratus, Holb., from the neighborhood of Poiladelphia, more than thirty in number. Many of them present important characteristics not hitherto noticed. The larger as well as a number of the smaller specimens, are of a chocolate brown or olive color above upon tbe carapax, with numerous blacii spots, the sternum brown, micgled with yellow ; iris golden ; upper part of head olive, with numerous small dark colored macukc ; two yellow vittte, passing one above, the other beneath the eye; barbels in both sexes. The differences between the male and the female are strongly marked, and may be presented as follows : Male. Female. Sternum more narrow and more con-Shorter (^ an inch) carapax higher, cave; tail much larger; shell more broader and more oval ; outline of disk depressed, especially in its posterior oval, somewhat compressed at the sides; half: portion of sternum behind ab-snout more acute ; gular plate more dominal plates, more quadrangular in elongated ; anal scutes longer, posterior shape. axillary plates larger. Dimensions. Length of carapax 4J Dimensions. Length of carapax 4 inches (Fr.); breadth at middle 3 inches; inches; breadth 3 inches; length of length of sternum 3 inches; greatest sternum3inches31ines;greatestbreadth breadth 2 inches. 2 inches, 3 lines. Posterior part of sternum slightly moveable in both, much less moveable than the anterior ; both male and female provided with scales upon the posterior part of the hinder extremities ; carapax of both sexes spotted. Habilat. Found abundantly near Philadelphia. Young. Differences betiveen male and female. Male. Female. Carapax of male more tectiform ; Carapax much depressed at its narrow in front, broader posteriorly; middle ; more rounded at the sides and outline of shell less distinctly oval ; broader anteriorly ; snout of female portion of sternum posterior to ab-more acute; sternum longer; anal scutes dominal plates more quadrangular, tail_ longer, much larger. Dimensions. Length of carapax SJ Dimensions. Length of carapax 3 inches; greatestbreadth 2 inches 7 lines; inches 7 lines; greatest breadth 2Hnch-length of sternum 2 inches, 7 lines ; es; length of sternum 2 J inches; greatest greatest breadth 2 inches 5 lines; greatest breadth 2 inches 5 lines; greatest length length of portion of carapax behind of posterior part of carapax behind ab-abdominal plates 1 inch 3] lines ; dis-dominal plates 1 inch 1 line ; distance tance between posterior margin of anal between posterior margin of anal scutes scutes and posterior margin of marginal and posterior margin of marginal plates plates 6 lines. 72 lines. ' Both sexes ash color, brown or olive above, with numerous dark colored spots; sternum yellow, or black, or brown mingled with yellow ; soft parts beneath ash mingled with white, yellowish or reddish mingled with yellow ; head olive colored; two yellow vittae, one passing above, the other beneath the eye ; iris golden ; barbels in both sexes and scales upon the posterior part of the hinder extremities. Habitat. Same as former ; hybernate in great numbers together, Mr. Vogt having turned out 239 from one hole. They are associated in hybernating with Tropidonotus sipedon and ordinatus, and Rana pipiens or Bull frog ; never with the Chelonura serpentina, or snapper, which is always found alone. Younger specimens. Shell strongly carinated and marked with dark colored radiating lines resembling in form those of Unio radiata ; no spots; contour of shell in females oval ; specimens 2\ inches and 2 lines in length. The varieties indicated above may be described as follows: Type. Predominating color, dusky ash above, with marblings of yellow, more especially along the sides ; head olive, with a few small yellow spots ; no yellow
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