LUDLOW FORMATIONS OP THE WEST OF ENGLAND. 377 



same jaw. There is a great variety in the size of different examples, 

 the smallest being only | line in length, while the largest is 2^ lines 

 long and |- line wide. 



This form approaches very closely to the S. niagarensis, H., from 

 the Niagara formation of Canada; but it is less inciirved, and gene- 

 rally a wider and larger speeies. It is the most abundant of any 

 of the Annelid jaws, and occurs in all the localities of the Wenlock 

 formation in very excellent preservation. 



Loc. and form. Much Wenlock ; Iron Bridge ; AVren's ISTest, 

 Dudley : Wenlock group. 



Genus Neeeidavfs, Grinnell, 1877. 



Nereidavijs antiguus, Hinde. (PI. XIY. fig. 21.) 



Jaw elongated, widest at the posterior extremity and gradually 

 tapering to the anterior obliquely projecting hook ; the central por- 

 tion slightly concave ; the basal margin curved ; the nearly straight 

 upper margin carnes numerous minute crenulations. The reverse 

 or under surface gently convex, and near the posterior end an oval 

 aperture. Length 1 line ; greatest width | line. 



Loc. and form. Iron Bridge, Salop : Wenlock group. 



Summary. 



Of the 27 forms mentioned in this paper, 21 are found only in the 

 Wenlock group ; 4 are common to the Wenlock and Ludlow, and 

 2 are restricted to the Ludlow group. There are in the Wenlock 

 strata 8 forms which have already been described from the Ameri- 

 can rocks ; of these, 2 are met with in the Cincinnati and Clinton 

 groups as weU as the Wenlock, 3 appear in the Cincinnati and 

 Wenlock and are absent from the Clinton, and 3 are present in the 

 Clinton and Wenlock and not in the Cincinnati group. Two of the 

 forms from the Ludlow group are also present in the American 

 rocks ; one of these is present in both the Cincinnati and Clinton, the 

 other in the Cincinnati group only. The close relationship of these 

 Annelid remains in such widely separated localities is not only shown 

 by the number of the forms which are identical, but also by the 

 very general resemblance which exists in those forms which are 

 here provisionally described as new. 



EXPLANATION OF PLATE XIV. 



Fossil Annelid Jaws from the Wenlock and Ludlow Formations. 



Fig. 1. Eunicites curtus, H. : X 12. Much Wenlock. 



2. (Enonites rcgularis, H. : X 12. Dudley. 



3. naviformis, H. : X 12. Dudley. 



4. prceacutus, H. : X 12, Much Wenlock. 



6. insignificans, H. : X 16. Ludlow. 



6. ctcneatus, yar. humilis : X 16. Iron Bridge, Salop. 



