370 G. J. HINDE ON ANNELID JAWS FROM THE WENLOCK AND 



rather than as presenting exact zoological arrangement. Indepen- 

 dently of the difficulties arising from the detached positions of the 

 particular jaws which compose the mouth-apparatus of the same 

 animal, it would appear, if we may judge from their great variations 

 in existing Annelids, that these organs are very insufficient for a basis 

 of classification. On this point M. Claparede, one of the greatest 

 authorities on recent Annelids, makes the following remarks * : — " If 

 it is possible to make use of the jaws in a certain measure as cha- 

 racteristic of the tribal divisions, on the other hand their employ- 

 ment ax^pears impossible, or at least very difficult, for the limitation 

 of the genera ; and I acknowledge that this fact surprises me. On 

 one hand very different jaws are met with in the same genus ; on the 

 other, identical jaws are frequent in different genera." 



As there is every indication that the Silurian Annelids possessed 

 the same variations in their mouth-apparatus which thus charac- 

 terizes the living members of the same order, it will be seen that, 

 in the absence of other recognizable structures, much uncertainty 

 must inevitably attend the arrangement of these fossil jaws under 

 different generic divisions. 



In addition to giving descriptions of new forms, I have deemed it 

 useful to make brief references to show which have been already 

 described from the American rocks. 



ANNELIDA POLYCHJSTA. 



Genus Eunicites, Ehlers. 



EuNiciTES MAJOR, Hinde. 



Eunicites major, Hinde, Quart. Journ. Geol. Soc. vol. 

 plate xviii. fig. 1. 



The only English specimen of this species met with is less trun- 

 cate posteriorly, has more acute denticles, and is smaller than the 

 generality of the typical forms from the Cincinnati group. Its 

 length is 1\ line, width | line. 



Locality and formation. Wren's nest, Dudley : Wenlock group. 



Eunicites curtus, Hinde. (PI. XIV. fig. 1.) 



Jaw consisting of an oblong compressed plate, widest in the an- 

 terior portion, the posterior end truncate, the base nearly straight ; 

 on the upper margin a series of twelve denticles, the first six of which 

 are subequal, blunted, and nearly upright, and the others pointed 

 and directed backwards. Length 1 line, width | line. This form 

 is allied to E. varians, Grinnell, sp., but is shorter, more compressed, 

 and with fewer denticles. 



Log. and form. Much "Wenlock : Wenlock group. 



* Annelides Ch^topodes du Golfe de Naples, p. 24. 



