THE NAUTILUS. 25 



dinal more than half as long as the nymphal callosity; mus- 

 cular scars large, the anterior deeply impressed ; there is no 

 subumbonal cavity; pallial sinus short, extending forward 

 less than half the length of the shell, acute, subtriangular ; 

 margin of the valves smooth. Length of shell 158; height 

 135+ ; diameter of right valve 40 mm. 



A single slightly imperfect right valve was obtained on 

 Magdalena Island. Than its nearest recent relative, M. squa- 

 lida, it is larger, more rounded, much heavier, with a less 

 uniformly smooth surface, and more concentrated hinge. In 

 M. squalida the right posterior cardinal is less than one-third 

 the length of the nymph, and the pallial sinus somewhat more 

 than half as long as the shell. The type specimen is in the 

 National Museum collection. It seems to be the heaviest 

 Venerid of the coast except Tivela stultorum. 



Panope (generosa Gould var. ?) taeniata n. sp.? 



Shell in a general way resembling P. generosa, from which 

 it is best distinguished by a differential diagnosis. The shell 

 of taeniata, is more arcuate, more attenuated behind, less 

 squarely truncate, the valve more inflated, with more of a 

 cavity under the beak, with a shorter ligament, and with the 

 posterior adductor scar nearly circular, while in generosa it 

 forms an elongate oval; the anterior scar is also larger and 

 wider than in generosa. Length of shell six and three-quarter 

 inches, height three and seven-eighths, diameter of left valve 

 an inch and a quarter. Compared with generosa the dimen- 

 sions are as follows in millimeters. 



M. taeniata, Ion. 170, alt. 103, diarn. 60, truncation 65. 



M. generosa, Ion. 172, alt. 97, diam. 48, truncation 78. 



The left valve of taenwta, from which this description is 

 drawn up, has a narrow rounded low rib extending from near 

 the beak to the lower margin near the base of the truncation, 

 but none of the specimens of generosa show anything of the 

 kind. This, however, may be an individual mutation and re- 

 quires confirmation by other specimens. The valve described 

 was found on the beach, probably washed out of the deposit 

 from which the fossils were obtained. 



