72 Jones and Holl—On the Genus Primitia. 



11. — Notes on the Paleozoic Bivalved Entomostraca, No. VI. 

 Some Siltjman Species {Primitia). By Professok T. Eupert 

 Jones, F.G.S., and Dr. H. B. Holl, F.G.S. {With a Plate of 14 



New Species). 



[Annals and Mag. Nat. Hist., sec. 3, vol. xvi. December 1865.] 



IN this commimication, Professor T. Eupert Jones, and Dr. H. B. 

 Holl, propose an improved classification for certain forms of 

 Silurian Bivalved Entomostraca, hitherto placed in the genus 

 BeyricMa. This genus comprises three types of carapace-valves, 

 namely, " simplices," " corrugatge," and "jugos^." The first of 

 these groups, the simple or unisulcate, seems to the authors to be 

 deserving of generic distinction, since, among all the forms, they 

 find a persistent occurrence of the chief features, with a passage 

 towards Leper ditia, by the complete loss of the furrow, rather than 

 towards the two-furrowed, or real Beyricliice. 



The authors explain the several difficulties presented, in attempt- 

 ing a critical examination of these minute crustaceans, such, for 

 example, as their tendency to variation in form and ornament, their 

 alteration by pressure and chemical change, and many other causes. 



They have, nevertheless, been enabled to collect 11 species and 4 

 varieties of BeyricMa, 2 species of Cythereopsis, and 14 new forms 

 for which they propose to establish the new genus Primitia.^ 



III. — British Association. — Section C : Geology. 

 A New Crustacean from the Moffat Shales. 



ME. HENEY WOODWAED described and exhibited specimens 

 of a new Phyllopodous Crustacean from the Moffat shales 

 (Lower Silurian), Dumfriesshire. 



These anthracitic shales abound in the remains of Graptolites, but 

 other fossils are extremely rare. Two phyllopodous Crustacea have 

 been described from them by Mr. Salter, namely, Peltocaris aptychoides 

 and P. Harhiessi. 



The new form closely resembles a Discina, but has a sector of 

 l-6th of its arc removed in nearly every specimen, the segment 

 being separated from the rest of the disc-shaped shield by a line of 

 suture. The shield is slightly conical, and ornamented with fine 

 concentric lines ; there is no dorsal suture as in P. a^ptycJioides A 

 specimen from the cabinet of Mr. Carruthers shows the wedge-shaped 

 rostral portion in situ. 



The most perfect example measures seven lines in diameter. The 

 caudal portion is not preserved. As this form is quite distinct 

 from any other fossil shield-bearing crustacean yet met with, the 

 author proposed for it the generic name of Discinoearis, with the 

 specific appellation of Browniana, after Mr. D. J. Brown, of Edin- 

 burgh, who first drew attention to it. 



^ With some additional details, the diagnosis for " Beyrichise simplices," giTcn in 

 the Ann. Nat. Hist., ser. 2, vol. xvi., p. 85, serves for Frimitia. 



