THE ANATOMY, HABITS, AND EMBRYOLOGY OF YOLDIA 



LIMATULA, SAY. 



Yoldia limatula is widely distributed along the coast of Maine, and 

 large specimens are abundant. Their principal habitat, however, is 

 in the shallow coves and inlets, where the tidal currents sweep by 

 without entering. Here, soft mud has accumulated, and is constantly 

 being added to by sediment, and by the decay of the plants and 

 animals that are swept in from the surrounding sea and land. Speci- 

 mens are most abundant in water from one to five fathoms deep, and 

 probably never occur above low tide mark. 



During the two seasons of my stay at Casco Bay, Maine, Mr. C. 

 B. Wilson generously allowed me the free use of his equipment, 

 which was of great value to me. Previous to this, specimens from 

 Woods Holl, Mass., were furnished me through the kindness of Professor 

 W. K. Brooks, Mr. Richard Eathbun and Dr. James L. Kellogg. Most 

 of these specimens were collected by Mr. Vinal Edwards. 



My own work, like the work of Drs. Mitsukuri 8 and Kellogg 5 upon 

 this animal, has been carried on under the direction of Professor Brooks, 

 who has for many years manifested a great interest in this rather 

 peculiar lamellibranch. It is a pleasure to acknowledge my indebted- 

 ness to him. I wish publicly to acknowledge my indebtedness to my 

 wife, who has materially aided me in securing, tending and preserving- 

 specimens. 



ANATOMY AND HABITS. 



The distinctive characters for the genus Yoldia as given by Verrill 

 and Bush 17 are : " shell nearly smooth, compressed, lanceolate, gaping, 

 more or less prolonged and tapering posteriorly, with a poorly defined 

 wide rostrum, generally without carinations. The external ligament 

 is marginal, feebly developed, continuous under the beaks and not 

 much differentiated from the general epidermis. The chondrophore is 

 large, concave, and projects within the margin. The pallial sinus is 

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