ball: mollusca and brachiopoda. 353 



Puncturella (Cranopsis) expansa Dall. 



Plate 4, figures 5, 10, 11, 

 Rimula ? expansa Dall, Proc. U. S. Nat. Mus., 1896, 18, p. 10. 



Shell low, rounded, expanded ; apex small, prominent, subcentral, recurved to 

 the right ; foramen like an exclamation point without the dot ( !), the small end 

 anterior, the suture in front of the foramen inconspicuous, marked by a narrow 

 raised line on the interior of the shell ; anterior slope convex, gently rounded ; 

 posterior a little excavated ; sculpture of evenly spaced, similar, close, fine, 

 rounded threads overrunning radiating, rounded, little elevated threads of three 

 sizes, the larger starting at the apex, the others intercalary toward the periphery 

 as the interspaces widen ; margin of the shell slightly crenulated by the sculp- 

 ture ; interior smooth, yellowish white, the septum convexly arched without but- 

 tresses. Height, 10 ; length, 32 ; width, 26 mm. 



U. S. S. " Albatross," station 33.58, Gulf of Panama, in 555 fathoms, sand, bot- 

 tom temperature 40°. 2 F. ; and station 3407, off the Galapagos Islands, in 835 

 fathoms, ooze, bottom temperature 37°. 2 F. U. S. N. Mus. 122,966 and 122,967, 

 the latter being the figured type. 



This species recalls P. asturiana Fischer, but is larger, lower, and more ex- 

 panded, a thinner shell, and witli more delicate sculpture. 



This appears to be the largest species of the genus yet described. A verge is 

 present at the seat of the right tentacle in male specimens. 



ISOPLEURA. 



POLYPLACOPHORA. 



Eochitonia Dall, 1889. 



Lepidopleuridae. 



LEPIDOPLEURUS Risso. 



Lepidopletirus (Risso) Hist. Nat. Eur. Mcrid., 1826, 4, p. 267 ; not of Carpenter, 



1863. 

 Leptochiton, Gray, P. Z. S. Lond., 1847, p. 127 ; Carpenter (Ms.) Dall, Proc. U. S. 



Nat. Mus., 1878, 1, p. 314. 

 Lepidopletirus Sars, Moll. Keg. Arct. Norv., 1878, p. 110; Pilsbry, Men. Polypla- 



cophora, 1892, p. 2. 



The chitons of tlie deep soa and archibenthal regions almost exclusively be- 

 long to the present genus, and ]u-csout an extremely uniform appearance. 



VOL. XLIII. — NO. 6 23 



