PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 161 



ARTICDLATA. 

 VERMES. 



Genus SPIRORBIS Lamarck. 

 Spirorbis? dickhauti (sp. uov.). 



Shell discoid, one side being nearly flat and the other broadly um- 

 bilicate; volutions about five, partiallj^ embracing but all of them visible, 

 somewhat rugose but increasing in size with considerable regularity ; 

 peripheral side of the volutions flattened or gently convex, having a 

 single revolving raisedrline along its middle and another similar one 

 at each border, where it sharpens the angularity between the lateral 

 and peripheral sides; outer portion of both the lateral sides of the 

 volutions concave, and the inner portion convex, giving the last-named 

 portion a greater transverse diameter than the outer portion, the larger 

 part of which is embraced by the next succeeding volution ; aperture 

 small, round, and apparently, but not really, contracted. The cavity 

 being round, the outer portion of the test only partakes of the irregu- 

 larity described, and seems to have' been deposited as an encrustation 

 upon the first-formed inner portion, that of adjacent volutions seeming 

 to blend, obscuring the suture. Besides a considerable degree of rugosity, 

 the surface shows under the lens a peculiar granular or rather an 

 etched appearance. 



Greatest diameter of the full coil of the largest example discovered, 

 9 millimeters ; greatest diameter of the outer volution, near the aper- 

 ture, 2^ millimeters. (Museum No. 9073.) 



In size and general aspect this species resembles 8. rotulus Morton 

 sp., from the Cretaceous of New Jersey, but although doubtless con- 

 generic, it differs from that species in the character of its surface orna- 

 mentation, and in having a round instead of quadrangular aperture. 

 This shell is referred to the shell-bearing worms and not to the mollusca 

 on account of the peculiar character of the test. It probably does not 

 strictly belong to the genus Spirorbis, but it is regarded as at least a 

 closely related form. 



Position and locality. — Cretaceous strata near Little Eock, Ark., 

 where it was obtained by Mr. E. O. Ulrich, and also by Mr. H. E. 

 Dickhaut, in whose honor the specific name is given. 



CRUSTACEA. 



Genus CALLIANASSA Leach. 



Callianassa TJLRicni (sp. nov.). 



Hand quadrate, flattened; inner face less convex than the outer; both 

 upper and lower edges acute, the lower one more so thun the upper, and 

 finely crenulate; fixed finger slender, plain, its transverse section sub- 

 Proc. Nat. Mus. 80 11 Aug. S4, 1 § §0. 



