462 Benjamin Sharp 



red eyes were preseut in both Arca and Pectuncuhts. Gegenbaur also 

 sustains the fact that the genera possessed eyes. 



Fam. Cardiidae* 



I have had the opportimity of examining macroseopically the 

 mantle-edge of Cardium muricatum , C. edule and C. magnum. Will 

 and SiEBOLD , both state that Cardium possesses eyes , the latter goes 

 so far as to state, that the shining eyes are situated on the euds of con- 

 tractile tentacles ; which fringe the external openings of the two short 

 mantle-tubes (siphon) and are extraordinarily numerous. I do not know 

 the species examined by these authors , but I can state as regards the 

 species C. edule ^ C. muricatum and C. magnum , that not the slightest 

 trace of any such organ was present, and further I could find no trace 

 of a deposit of pigment. It is true, that the specimens that I examined, 

 had been in alcohol for a long time and the deposit of pigment or small 

 organs may have become destroyed. 



Fam. Veneridae, 



Venus mercenaria. When the liviug siphon is extended, it projects 

 but a few millimeters beyond the edge of the shell. When the siphon 

 is cut open, we find that the internai length is about 1,5 cm. The ex- 

 ternal surface of the siphon is brownish and toward the orifices of the 

 siphons it becomes peppered with black pigment being quite black at 

 the very end. Internally the siphon presents a yellowish color also 

 blackened toward the exterior opening. 



If the mouths of the two apertures of the siphon be examined, 

 they will be found to be fringed with fine processe» or tentacles measur- 

 ing about 1 mm in length. These tentacles are most numerous and best 

 developed at the edge of the brauchial siphon and very scarce and small 

 at the anal. A black line is seen to extend on the parti tiou which divides 

 the two siphons. 



When sections are made of the end of the siphon , so that the 

 wall is cut through parallel to its greatest length , we find on both 

 sides of the section , that is the external and internai surface of the 

 siphon, a layer of well developed and distinct columnar cells. This 

 layer of epithelium is thrown into numerous folds as is seen in fig. 4. 

 This layer of cells lies on the cutis , which is made up of connective 

 tissue and muscular fibers with distinct nuclei. In the middle of the 

 wall of the siphon are seen numerous parallel fibres, which, in connec- 

 tion with the retractor musale, serve to withdraw the siphon. 



