892 PROCEEDINGS OF THE NATIONAL MUSEUM. 



MYSELLA BARBADENSIS Dall. 



Mysella barbadensis, new species. 



(Plate LXXXVIl, fig. 3.) 



A. 25. Shell small, white, thin, inflated, ine(iuilateral, ovate, with 

 distinct beaks, rounded at both ends, with a couvexly arcuate basal 

 margin, the short posterior end somewhat attenuated; surface appar- 

 ently smooth, but not polished, maguilication shows a fine, even con- 

 centric striation; pallial scar linear, adductor scars small,- obscure. 

 Lon. 4, alt. 2.9, diam. 1.8 mm. 



This species recalls M. tumidula, but is rather longer, less inflated, 

 more equilateral, and has a different surface. A single left valve was 

 obtained. 



MYSELLA (PYTHINELLA) CUNEATA Verrill and Bush. 



Moutacuia cuneata Verrill and Busii, Proc. U. S. Nat. Mus , XX, 1898, p. 782, 

 pi. xci, fig. 4; pi. xciii, fig. 5. 



A. 2G. This species presents the concavely arcuate form which I believe 

 to be correlated with commensalism, and the groui) of species thus dis- 

 tinguished in Mysellaj for which I have proposed the name Pythinella, 

 has the same relations to the typical Mysella as Pythina has to Bornia, 

 Fseudopythina to JEryema, and Sindsiella to its associated genera. 



MYSELLA TUMIDA Carpenter. 



Tellimya tiimida Carpenter, Suppl. Rept. Brit. Assoc, for 1863 (1864), pp. 88, 97, 

 129; Proc. Acad. Nat. Sci., Phila., 1865, p. 58. 



B. 18. It has not hitherto been figured and I have given (Plate 

 LXXXVIl, fig. 7) a camera lucida outline from tlie type specimen for 

 comparison with the other west coast species. It is especially charac- 

 terized by its ^olid and tumid valves, rounded triangular form, and 

 strong hinge. Lon. 3.8, alt.. 3.2, diam. 2 mm. 



MYSELLA PLANATA Dall. 



Tellimya planaia Dall, in Krau.se, Beitr. Moll, fauna <les Boringsmecrs, Arch, 

 f. Naturg., LI, 1885, Pt. 1, p. 34, pi. iii, ligs. 6 a-d. 



B. 19. Dr. Krause's figures are not all equally characteristic, and I 

 give, therefore, a magnified camera lucida sketch (Plate LXXXVIII, 

 fig. 12) from one of his specimens which shows the hinge and outline 

 rather better. Lon. 5.3, alt. 4, diam. 2 mm. 



MYSELLA ALEUTICA Dall. 



Mysella aleutica, new species. 



(Plate LXXXVIl, fig. 6.) 



B. 20. Shell small, solid, ovate, white, smooth, covered with a polished 

 straw-colored epidermis with usually three or four concentric darker 



