8G REPORT 188-1. 



was from the Lower Silurian of Penwhapplc Burn, near Grirvan, Ayr- 

 shire ; and we wish to give it the name of Dipterocaris Etkeridgei, in com- 

 pliment to Mr. R. Etheridge, jun., who has worked so well among the 

 palaeozoic Phyllopods and other fossils. 



Whether or no the hinder cleft in Dipterocaris was ever occupied by 

 a triangular piece, lost after death, we cannot say. No direct evidence 

 supports the idea that there was a portion of the test filling in this 

 posterior notch ; but the elongate triangle defined by the radiating 

 furrows in Pholadocaris Leeii, and by ridges (?) in Ph. sp. (F. A. 

 Roemer's 'Aptychus'), seems to be an analogous feature. On the other 

 hand, the posterior notch in Dipterocaris may have had reference to the pro- 

 trusion of the abdominal somites, as suggested by Mr. J. M. Clarke, ' Amer. 

 Journ. Sci.' 3, vol. xxv. p. 124. Mr. Clarke, Joe. cit., considers it pro- 

 bable that the anterior cleft was also permanently open, for the convenient 

 protrusion of the cephalic appendages ; bat analogy with other Phyllo- 

 carida, and especially the abrupt termination of the concentric lines of 

 growth on the edges of the notch (as if the lines were continued on a 

 cephalic piece, as in allied forms), are our reasons for retaining the 

 views we have already expressed. 



DlPTEROCAEIS. 



JDvpterocaris pes-cervai Without Goniatites. Upper Devonian, New York State. 



„ vetusta With „ „ „ Hartz. 



„ proene "1 f „ „ New York State. 



„ pe/mce-desdaU l Without „ < „ „ ,, ,, 



„ Etheridgei J |_ Lower Silurian, Scotland. 



VIII. PTEEOCAEIS, Barrande, 1872. PL bohemica, Barr. ' Syst. Silur. 

 Boheme,' vol. i. Supplem. p. 464, pi. 25, figs. 25, 26. 



A single specimen (a cast) of this interesting form has been carefully 

 described by M. J. Barrande in detail. Its apparent relationship to 

 Aptychopsis and other fossil Phyllopods is pointed out ; its anterior, 

 triangular, apparently fixed, rostral piece, and its open and deep posterior 

 cleft, are described and figured, together with the radiate ornament of 

 the lateral pieces of this cast. The fossil is flat. Broadly obovate in 

 outline (outside the notch). Length 12 mm., width about 12 mm. 



In general shape Pterocaris corresponds with Dipterocaris, and indeed 

 exhibits the cephalic or rostral piece, which has been lost from the other 

 specimens known. The ornamentation, however, as preserved on the 

 cast (apparently of the inner or lower side) is peculiar, being strice 

 radiating from a straight line which reaches along the greatest length of 

 each wing or lateral piece, and is parallel to the median line of the 

 isthmus ; or rather the striae look as if they would converge centrally on 

 the isthmus, if they were not interrupted by the longitudinal line on each 

 wing. In Dipterocaris the ornamental lines are concentric with the 

 isthmus. 



From the quartzite of D d 2 (Lower Silurian = Llandeilo and 

 Caradoc) at Mount Drabow, with Gary on bohemicum, Zonozoe, 2 spp., 

 and Cytheropsis testis. 



The last-mentioned fossil is an internal cast apparently, as M. 

 Barrande suggests, of some half-shut Entomostracan bivalve ; side-view 

 elongate, subelliptical, with a straight dorsal edge and neatly rounded 



