252 NEW- YORK FAUNA — MOLLUSCA. 



Balanus interruptus. 



(STATE COLLECTION.) 



Description. Shell conic-truncate, somewhat broader than high, more oblique on one side, 

 gregarious. Aperture oval; the superior valves semi-concentrically striate. Side with very 

 prominent rounded ribs, often bifid at the base ; each rib divided into 4-6 segments, which 

 are subimbricate : about midway, in many specimens, the segments are short and crowded. 



Color, ashen gray. 



Height, 0"3. Largest diameter of base, 0-5. 



This species is found adhering to rocks in Long-island sound. It appears to be allied to 

 B. geniculatus of Conrad, but its ribs are destitute of the two angular elevations. 



Balanus eburneus. 



PLATE XXXIV. FIG. 320. 



(STATE COLLECTION.) 



B. eburneus. Gould, Invertebrata of Mass. p. 15, fig. 6. 



Description. Shell isolated, conical, robust, smooth and polished, with angular elevations 

 and minute horizontal and vertical rugae, oblique on one side and more vertical on the other. 

 Aperture jagged, beaked on one side. Base oval or rounded, either partially or entirely 

 closed, concentrically striate ; the inner side of the base vertically striate, the pieces united by 

 horizontally pectinated edges. The two upper opercular valves largest, triangular, concen- 

 trically striated and reticulated ; the lower emarginate. 



Color. Ashen white ; lip often with a pinkish hue ; valves greenish. 



Height, 0-4-0-7. Diameter of base, 0-6-0-9. 



This species is not uncommon on floating timber on the northern shores of Long island. I 

 have received specimens from the northern coast, under the name of B. ovularis, from which, 

 however, it appears widely to differ. It is the largest species I have met with on the coast 

 of New- York. It is never gregarious. In my notes I had named it B. democraticus, but it 

 appears to be identical with the species described by Dr. Gould under the name cited above. 



