150 INVERTEBRATA OF MASSACHUSETTS. 



valves, sometimes arranged in stripes ; such a stripe will usually 

 be found at a little distance on each side of the keel, while the 

 keel itself has a stripe of crimson spots, occasionally replaced by a 

 yellow spot. It is frequently incrusted with a black foreign sub- 

 stance. Margin coriaceous, coated with a red and white dust ar- 

 ranged in alternate stripes. Triangular areas generally well 

 marked. Interior bright rose-red, becoming fainter at the mar- 

 gins of the valves. Length ^ inch, breadth j% inch. 



Found adhering to stones dragged from the deep by kelp ; 

 also in the maws of fishes. 



It is not difficult to distinguish at sight well-marked individuals of 

 this species from those of C. fulminatus. But there are intermediate 

 specimens which it is not easy to pronounce upon, hi general, this 

 species is smaller, more solid, more convex, the valves more beaked, 

 lines of growth more deep, the zigzag lines never appearing, though 

 the posterior margin of the valve is sometimes dotted with white and 

 red. The impunctured or ungranulated surface, however, is the best, 

 as it is a constant, characteristic. 



That this is the C. ruber of Lowe and Sowerby, 1 think there can 

 be no question, though it may not be C. ruber of other authors. The 

 figure in Pennant, "Brit. Zool.," pi. 36, f. 3, also represents accu- 

 rately most of die adult specimens, though it is quoted by authors as 

 C. IcBvis, which is distinguished by its finely reticulated margin. 



Chiton albus. 



Shell small., cllijjtical, valves carinaied and yartially beaked, 

 minutely granulated ; margin beaded. 



Figure 27. 



State Coll., No. 133. Soc. Cab., No. 973. 



Chiton albus, Montagu; Test. Brit., A. Sowerby; Conch. //^MS^, 99, 99 a, 100. 



Brown ; Conch, of Great Brit., S^c. pi. 35, f. 2. 

 Chiton aselloides, Lowe; Zool. Journ., ii. 103, t. 5. f. 3. Wood; Suppl., pi. 1, 



f. 9. 

 Chiton sagriniitus, Couthouy ; Bost. Journ. Kat. Hist., ii. 82. 



Shell small, elongated-oval ; covered with a bluish-black pig- 

 ment, which easily rubs oif, and leaves the ground yellowish or 

 ash-colored ; surface beautifully granulated, under the microscope, 



