116 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



bottom of sand, mud and shells, temperature 75.8° F., and is the 

 unique specimen. It measures — length, 7 mm.; diameter, 1 mm.; 

 anterior aperture, 0.85 mm. ; apical aperture, 0.5 mm. 



This httle Cadulus is removed from a lot of C. nitidus taken in 

 Mayaguez roadstead. Its affiliations would appear to be with C. 

 carolinensis, from which it differs chiefly in being smaller. In general 

 shape it is of the group of Caduli that have no definite equator nor 

 prominent localized swelling. Some uncertainty attaches to the 

 apical features, which I hope may be removed by receipt of better 

 material. 



The following five species are characterized by a bent or crooked 

 appearance, chiefly caused by the obliquity of the anterior aperture, 

 together with an anterior position of the equator — a ''dog-tooth" 

 shape so often referred to by authors: Cadulus rusMi, C. pandionis, 

 C. watsoni, C. vulpidens, C. providensis. 



CADULUS (PLATYSCHIDES) RUSHII Pilsbry and Sharp. 



1898. Cadulus (Gadila) rushii Pilsbry and Sharp, Tryon's Man. Conch., vol. 17, 

 p. 1(58, pi. 27, figs. 94-97. 



The shell is moderately solid, the typical subspecies being large 

 (11.5 mm.), another subspecies smaller (8.3 mm.). It is moderately 

 curved, chiefly posteriorly, the convex side evenly arched throughout, 

 though slightly accentuated at the equator, which is about one-fourth 

 the distance from the anterior aperture. The concave side is nearly 

 straight in the anterior half, but decidedly arched posteriorly; the 

 section of gi'eatest diameter is about one-fourth distance back of the 

 anterior aperture, where the shell has a diffused moderate swelling, 

 though not bulbous or gibbous. The entire shell is dorso-ventrally 

 compressed, but less so at the two apertures. The larger aperture 

 is oblique with a rounded peristome. The apical orifice is a little 

 oval, with the rim indistinctly cut by four slits, leaving as many low 

 flat lobes, the dorsal and ventral ones being the broadest, the former 

 with an obtuse angle, the latter flat-topped and slightly flaring out. 

 These features can rarely be observed in any single specimen, owing 

 to accidental breaks. Measurements are: 



Length, 11.6 mm.; maximum diameter, 2 by 1.8 mm.; anterior 

 aperture, 1.6 by 1.4 mm.; apical aperture, 0.6 by 0.53 mm. (Type 

 of Cadulus rusJiii rushii.) 



Length, 8.3 mm.; maximum diameter, 1.3 mm.; anterior aperture, 

 1.2 mm.; apical aperture, 0.8 mm. (Type of C. r. arne.) 



This is a fairly deep-water species, ranging from off Cape Hatteras 

 to Nantucket, in 293 to 1,060 fathoms. 



C. rushii occupies an intermediate position between C. agassizii, 

 with the flattened, wide flaring posterior aperture of that species, 



