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 



