AND EMBRYONIC FORMS 413 



Unio spmosus, Lea. Trans. Amer. Phil. Soc, vol. vi. pi. 16, fig. 50. Obs. vol. ii. p. :r, 



Branchml uterus occupies the whole length of the outer branchise, the ovisacks 

 being filled with ova not developed enough to give the form of the shell. BranoHm 

 very large, rounded below, the interior ones much the larger, free nearly the whole 

 length of the abdominal sack. Palpi very large, suboval, united nearly half way 

 down the posterior edges. Mantle thickened and somewhat doubled at the basal 

 edge, having minute papillae below the branchial opening. Branchial opening with 

 numerous small, obtuse, subcorneal, light-brown papillae. Anal opening with regular 

 small, closely-set, light-brown papilla. Super-anal opening long, slightly colored on 

 the inner edges and united below. Color of the mass whitish. 

 Altamaha River, near Darien, Georgia, J. Hamilton Couper, Esq. 

 Bemarks.-The form of the ovisack is somewhat peculiar, being obliquely rounded 

 at the lower end and pointed at the upper. It is very flat and white, a half inch 

 long and about an eighth wide in the middle. A single ovisack contains an im- 

 mense number of very small, white ova which seem to be arranged in regular 

 oblique rows. In some specimens the ovisacks were found in the cavity over the 

 branchiae, evidently having passed from the uterus on their way out above. They 

 were lying there superimposed on each other in great number. The cicatrices made by 

 muscular attachment in the shell are very deep, that of the mantle unusually so and 

 particularly below the branchial opening, where there is quite a lunate cicatrix enlarged 

 on the line of the palleal cicatrix. There are also deep cicatrices running from the 

 base of the spines, inside, towards the palleal cicatrix, and generally enlarging in 

 the latter. A half-grown specimen presented the two lower (4th) spines perfectly 

 hollow to the end, they being not more than half the usual length. The hole on 

 the interior of both valves is perfect. In another specimen there was but one long- 

 spine, and this had a long extension of the side of the mantle, like the finger of a 

 glove, which passed from the edge of the mantle, united to it for a quarter of an 

 inch and then passed under the arch of the spinal cavity into the spine to the top 

 This finger-like extension being quite an inch long. 



Unio dolabr^formis, Lea. Trans. Amer. Phil. Soe, (2), vol. vi. pi. 2-t, fig. 113. Obs. vol. iv. p. 103. 

 Branchial uterus occupies the posterior portion of the outer branchiae in fifteen to 

 twenty large ovisacks, very like cariosus, the inferior border being blackish. Bran, 

 chia very large, round below, inner ones the larger, united the whole length of 

 abdominal sack, except at the posterior point where the hole is so small as scarcely 

 to be detected. Palpi very large, suboval, united half way down the posterior 

 edges. Mantle rather thick, with a broad, thickened margin, colored along the 

 posterior basal portion. Branchial opening large, with numerous large and small 

 reddish-brown papilla?. Anal opening rather small, with numerous very small. 



105 



