732 PROCEEDINGS OF THE NATIONAL MUSEUM. voi,. xxvii. 



Among the species described as Allerisma which probably belong 

 with PleuropliOi'ella ixqjiUosa, none is nearer than Allerisma costatum. 

 I have no specimens of that species with which to make direct com- 

 parison, but Meek's description shows the following differences, 

 though the resemblance is so marked that liut few can be pointed out. 

 The concentric folds m. Pleiiropliorella jjapillona are not so strong or so 

 regular, and the lunule is apparently more deeply concave, for Meek 

 only mentions this feature casually in AllerisiiKi. costatum, while it 

 could not but be the subject of more particular comment if it were 

 anywhere near as deepl}^ indented as in the Texan form. The latter 

 is dikewise not so elongate transversely nor does the anterior end pro- 

 ject so strongly. 



CLAVULITES", new genus. 



In the Burlingame shale at Howard, Kansas, occurs an interesting 

 little shell whose resemblance to the Dental iidte is rather striking, and 

 yet some of whose characters are so peculiar as to warrant its consid- 

 eration as a genus distinct from any at present referred to the family. 

 But a single species is known. 



CIdtmUtes is founded upon a small, curved Dentalioid shell resem- 

 bling the Plagloglyptd section rather than Dentallum in the strict 

 sense. The surface is marked b}^ line, flcxuous, obliquely transverse 

 line, as in PhA<jlo(jlijj>ta ; but the character of especial importance is 

 the presence on the concave (dorsal) side of a linear ridge or callosity 

 over which the line pass with a strong anterior deflection. It is dif- 

 ficult where, as here, ])ut a single species is known to distinguish 

 between the strictly generic and specific characters, but it is probable 

 that the annulated surface and the dorsal callosity will remain the dis- 

 tinctive generic characters of Clavulltes. 



Genotype. ^ — CiavuUtes hoinardensis. 



CLAVULITES HOWARDENSIS, new species. 

 Plate XLVII, figs. 4, 5, 6, 7, 8, 9, 10, 11. 



Shell small, rapidl}" tapering, often strongly curved. Cross section 

 circular. Along the dorsal or concave side the shell is thickened into 

 a linear welt or ridge, which varies in prominence in different indi- 

 viduals, but is always present and always dorsal. The callosity is not 

 altogether due to a thickening of the shell, however, because it can 

 sometimes be detected upon internal casts. 



This structure was doubtless produced b}^ a lobe of the peristome 

 quite different from anything known in Dentalhnn, and represents 

 differences in organization sufficiently marked to show that Claindltes 

 should bo considered a distinct genus, and possibly the representative 

 of a distinct famil}'. The surface of CiavuUtes hovjardensis is crossed 

 by regular, subequal, flexuous, obliquely transverse lira?. Upon the 



« From davulus, a little nail or tack. 



