10 PROCEEDINGS OF THE ACADEMY OP [1881. 



two points to the summit ; usually of minute sand and comparatively 

 smooth. One oblique form noticed (No. G), approaching D. constricfa. 



1. Shell 0.18 mm. long ; 0.108 broad ; oral end 0.06 broad. 



2. Shell of same size, but with a short neck, slightly erected and 



undulant at the border. 



3. Shell 0.18 mm. long ; 0.114 broad ; oral end 0.048 broad. 



4. " 0.198 " " 0.103 " " 0.06 " 



5. " 0.18 " " 0.114 " " 0.06 " 



6. *' 0.163 " " 0.09 " " 0.06 " 



Nos. 1-3 of fine sand, and smooth ; Nos. 4-6 of coarser sand. 



The slide with food of Eremyzon succetta. The material apparently 

 consisted of the superficial sediment of the water, and contained entomos- 

 tracans, rotifers, dipterous larvae, desmids, diatoms, etc., together with 

 the following : 



DiPFLUGiA GLOBOLOSA. Shell 0.15 mm. long, 0.138 broad; oral end 

 0.078 broad. 



DiFFLUGiA L0B08T0MA. Shell with trilobed mouth, 0.09 mm. long, 

 0.078 broad ; mouth 0.03 wide. Several measvired of the same size ; 

 others slightly smaller. The most common species present. 



DiFFLUGiA PYRiFORMis. Shell 0.43 mm. long, 0.31 broad, at mouth 

 0.09 broad. 



Arcella vulgaris. Variety with pitted shell. 



Arcella discoides. Shell 0.18 mm. broad, mouth 0.036 wide. Another 

 specimen 0.15 broad, with mouth 0.054 wide. 



Another rhizopod shell observed, was diflferent from any pre- 

 viously noticed. The shell had the form of that of Arcella dis- 

 coides, with no trace of the structure characteristic of that of 

 Arcella, but composed of a nearly colorless or pale yellowish 

 chitinoid substance, incorporated with minute spherical granules 

 of uniform size, darkly outlined, scattered irregularl}^, isolated, or 

 in little groups or chains, straight or irregular, and in pairs, or up 

 to five in number. The specimens measured about 0.105 mm. 

 broad, with the mouth 0.03 wide. A chain of five granules of the 

 shell measured 0.009 mm. long. 



It is certainly an interesting observation of Mr. Forbes, to dis- 

 cover that the young suckers should use the rhizopod shells to 

 olitain as nutriment their little stores of delicate protoplasm. 



January 11. 

 Dr. John L. Le Conte in the chair. 

 Eighteen persons present. 



A paper entitled "Descriptions of new species of Terrestrial 

 Mollusca of Cuba," by Rafael Arango, was presented for pub- 

 lication. 



