﻿50 DESCRIPTIONS OF EMBRYONIC FORMS. 



Anodonta Ferussaciana, Lea, fig. 85. Subtriangular ; dorsal line long and straight ; side margins slightly 

 inflated above, compressed and flattened from above the centre, forming a very obtuse angle at base ; 

 basal margin rounded; no hooks apparent; color darkish brown. Columbus, Ohio. 



Anodonta imbecilis, Say, fig. 36. Subtriangular; dorsal line very long and very slightly curved; side 

 margins inflated above, gently curved towards the base ; basal margin nearly circular, furnished with a 

 hook ; color light brown. A hook is placed on the inside of each valve at the base. Fig 36 a hook 

 much magnified, triangular, broad at the base, acute at the point, with numerous regular granules over 

 the whole surface. Columbus, Ohio. 



Anodonta edenttjla, Lea, fig. 37. Subtriangular ; dorsal line very long and straight ; side margins much 

 inflated above, slightly flattened below, forming a very obtuse angle at base ; basal margin rounded and 

 furnished with a hook ; color brown. A hook is placed on the inside of each valve at the basal point. 

 Fig. 37 a represents both valves well opened and displaying the hook on each valve. Fig. 37 b , hook very 

 much magnified, rather broad at the base and terminated with three points. There are four rows of 

 granules at the base, the two centre ones only extending to the end. Columbus, Ohio. 



Anodonta undulata, Say, fig. 38 a . Subtriangular ; dorsal line very long and straight ; side margins 

 above and middle much inflated, presenting a segment of a circle, flattened towards the base; basal 

 margin rounded at the point, which is obscurely serrate and furnished with a hook ; color bright brown. 

 A hook is placed on the inside of each side of the valve at the base. Fig. 38 is a highly magnified 

 view of the wide open shell with the soft parts displaying the attachment to the inside of the valve 

 and the serrated hooks,* which were very large and exceedingly well defined. Fig. 38 b is a view look- 

 ing directly into the interior, and displays the two hooks in contact at the points. Fig. 38 c represents 

 both hooks, which are broad at base and are nearly triangular in form. They are covered entirely over 

 with granules. The lower one is the better representation. Fig. 38 d is the branchial ovisack magnified 

 five diameters, with the young shells, extruded from the ova, attached at the dorsal line to the exterior 

 of the sack. The hooks were apparent in every individual. A few ova still remained within the 

 sack which was milk-white and not diaphanous. Schuyler's Lake, New York. 



Ovum of Unio subangulatus, Lea, fig. 39, represents a nearly round ovum greatly enlarged. It was 

 taken from the branchial uterus, on the last day of October, and evidently was far from being very much 

 advanced in incubation. This species probably spawns in the spring as most of the Uniones do. There 

 were four nucleola composed of pale yellow granules. The albumen surrounding them was transparent. 

 Chattahoochee River, Georgia. 



* This figure and the following one are drawn on the stone more massive than they ought to have been. 



