20 G. O. SAES. [No. 7. 



claws (fig. 5), affixed to a short conical projection issuing from the 

 tip of the tail, are rather elongate and slender, very slightly curved, 

 and armed in their basal part with a regular comb-like series 

 of about 12 spines, the remaining part being but very minutely 

 ciliate along the concaved edge. The anal denticles number on 

 each side from 9 to 12, successively increasing in size toward 

 the extremity of the tail, the outer ones rather large and sharply 

 curved. The part of the body adjoining the tail is considerably 

 curved, the dorsal edge forming two well marked obtuse angles. 

 To the anterior angle is appended a rather long falciform pro- 

 cess, curving upwards; and at the posterior angle occurs another 

 somewhat smaller process, generally in close contact with a ra- 

 ther broad, arcuate fold, projecting inwards from the posterior 

 part of the carapace and terminating at the tip of its posterior 

 projection. Both these processes serve to close the incuba- 

 tory cavity, or matrix, behind, the young being only allowed to 

 escape, when the body is very strongly curved beneath and pro- 

 jected beyond the valves inferiorly. 



As to the inner organs, the cylindrical alimentary tube, 

 filled with yellowish or greenish contents, can be at once seen 

 through the shell. It is furnished at the anterior extremity with 

 2 large incurved coecal appendages (see fig. 2), and posteriorly 

 enters the tail, becoming somewhat dilated before joining the 

 muscular rectum. 



The heart, located as usual dorsally in the anterior part of 

 the trunk, is rather small and of a simple oval or pyriform 

 shape, with a single venous opening on each side. 



The ovaries, when fully developed, are rather large, cover- 

 ing a great part of the intestinal tube at the sides, and of a 

 dark greenish colour. The ova entering the matrix, are com- 

 paratively small and in some cases very numerous (see fig. !)• 

 The colour of the animal is pale yellowish or ochraceous, 

 with a slight olive tinge in the dorsal part. Moreover, the valves 

 are ornamented with a few irregular patches of golden yellow. 



Biological Observations. — The first specimen of this form 

 I observed on the 23rd June 1886, in a small aguary prepared 



