LUDLOW FOBMATIONS OF THE WEST OF ENGLAND. 375 



margin, which extends to the cavity passing just below the upper 

 hook. Length IJ line; width nearly | line. 



This form is allied to the preceding, A. ecctensus, but differs in the 

 spike at the corner of the base, the less extension of the upper 

 margin, and the fewer denticles. 



Arabellites spicatus, var. contractus. (PI. XIY. figs. 14 & 15.) 



Jaw oblong, convex, with a relatively elongated anterior hook, 

 not in the same i^lane with the anterior portion of the jaw, but 

 obliquely curved (the point of the hook is wanting in the specimen) ; 

 the posterior extremity is obliquely truncate ; there are from 7 to 

 10 small denticles on a slightly elevated ridge, which extends in an 

 oblique direction below the upper ridge of the jaw. On the reverse 

 or inner side there is a deep groove traversing the jaw subcentrally, 

 and extending to the oval aperture of the cavity below the hook. 

 Length 1 line. 



This variety differs from A. spicatus in wanting the extension of 

 the upper margin, and in the different position and smaller number 

 of the denticles. 



Log. and form. Much Wenlock : Wenlock group. 



Ababellites sulcatus, Hinde. 



Glycerites sulcatus, Hinde, Quart. Journ. Geol. Soc. vol. xxxv. 

 p. 380, pi. xix. fig. 1. 



The specimens in the Cincinnati group, from which I described 

 this species, presented only the reverse or inner side of the jaw, and 

 led me to suppose that it consisted merely of a simple curved hook 

 similar to that present in the existing genus Glycera. I have now, 

 however, been able to extract some of these jaws quite free from 

 the rock matrix, and find that they possess on the front or outer 

 surface a row of minute denticles, which would indicate that they 

 more closely approach the genus Arabellites : and I therefore pro- 

 pose to place them under the latter genus. Examples of this form 

 quite undistinguishable from specimens from the Cincinnati group 

 are by no means unfrequent in the English Silurian. 



Log. and form. Much Wenlock; "Wren's Nest, Dudley : Wenlock 

 group. Ludlow : Upper Ludlow group. 



Aeabellites obtusus, Hinde. (PI. XIY. fig. 16.) 



Jaw subtriangular, compressed, the base straight, with a short 

 blunted extension below ; the anterior tooth curved, followed by a 

 series of five blunted denticles. Length ^ line. 



This small form appears to be aUied to A. crenulatus, from the 

 Cincinnati group, from which it differs in the form and number of 

 its denticles as well as in its smaller proportions. 



Log. and form. Much Wenlock : Wenlock group. 



Arabellites anglicus, Hinde. (PI. XIV. fig. 17.) 



Jaw somewhat crescentiform, compressed, the anterior border ox- 



