THE NAUTILUS. 27 



Mrs. W. H. Eshnaur satisfied our curiosity and excited our surprise 

 by sending several of these shells in situ, and, of all places, on the 

 valves of Glottidia albida Hinds ! The latter were well grown, and 

 the Crepidula exactly covered the outside of the valve, some speci- 

 mens having a Crepidula on both valves, others only on one. 



It is well known that the brachiopod in question burrows in the 

 sand ; a mucus which exudes from it consolidates the adjacent sand 

 into a 6ort of tube, from which the distal margins of the valves pro- 

 trude a little. Hence the Crepidula could satisfy its instinct for 

 being on the inside of things, yet not out of reach of food, and the 

 brachiopod was supplied gratis with a well-fitting cuirass or acces- 

 sory armor, both benefiting. This peculiar-looking Crepidtda might 

 appropriately take the mutational name of glottidiarum, in case one 

 wishes to refer to it briefly. It forms a striking instance of the way 

 in which form is dependent in this genus on situs, a subject some- 

 body would find it profitable to work up. 



NOTES ON A COLLECTION OF SHELLS FROM BASS LAKE, INDIANA. 



BY FRANK COLLINS BAKER. 



Some months ago my assistant, Mr. Frank M. Woodruff, made a 

 small collection of shells at Bass Lake, Indiana, which seems of in- 

 terest enough to list. Bass Lake is a beautiful sheet of water, the 

 clear, crystal depths of which teem with fish and mollusks. The 

 specimens are particularly large and fine. 



Anodonta grandis Say. The specimens obtained are the form 

 called sahnonia by Lea. As stated by Simpson, this form is nearly 

 always blistered and scaly. The salmon color is very beautiful in 

 some specimens. 



Anodonta grandis var. footiana Lea. 



Sphcerium oceidentale. 



Calyculina truncata. 



Pisidium abditum Haldeman. 



Vivipara contectoides Binney. The individuals from this locality 

 vary from uncolored to distinctly four-banded, and are notably large 

 and fine. 



Amnicola limosa Say. 



Atnnicola limosa var. parva Lea. 



