402 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



Shell cordate, with an ohtuse prominent posterior dorsal keel ; 

 posterior side deeply excavated ; striae numerous, concentric, and ir- 

 regular. 



In young specimens the form is less gibbose ; the small dental 

 processes are very distinct, but the large tooth has little of the im- 

 portance which it afterwards attains, it not having acquired the coni- 

 cal projecting form as in the adult state. 



This shell does not appear to have been described, although it 

 closely resembles a figure published by Catullo * of a cast of a shell 

 named Cardium triquetriim by Wolfen f, from the Jurassic strata of 

 Antello near Cardonino. The shells figured by Pusch, Polens. Pa- 

 leont. t. 7. f. 8, 9, under the names Isocardia exaltata and I. ven- 

 tricosa, have some affinity vsith our shell, and may belong to the same 

 genus. 



This shell has been provisionally referred to Cardilia J, but ha- 

 ving been enabled, by the kindness of Mr. H. Cuming, to examine 

 specimens of that interesting genus of M. Deshayes, we are enabled 

 to state that the position of the ligament in the two genera is very 

 distinct ; in Pachyinsma the hgameut is external, in Cardilia it is 

 internal, seated on a somewhat complex spoon-shaped tooth ; the 

 position of the posterior muscle is however in both genera very ana- 

 logous, being placed in Cardilia on a prominent laminar plate, repre- 

 senting the auriform process which supports the same muscle in 

 Pachyrisma. 



Locality. — From the Great Oolite in the vicinity of Minchinhamp- 

 ton and Chalford. 



2. Observations on Dudley Trilobites. Part 2. By Thomas 

 William Fletcher, F.R.S., F.G.S. &c. 



Genus Cybele. 



Two species of Trilobites belonging to the interesting genus Cybele 

 of Loven § are occasionally fomid at Dudley, the C. punctata and C. 

 variolaris\ perfect specimens of either species being very rare. These 

 species were figured from Dudley specimens, probably then unique, 

 by M. Brongniart, in his ' Histoire naturelle des Crustaces fossiles,' 



* Saggio di Zoologia Fossile, de T. A. Catullo, t. 1. f. D, E, F, f. 2 A. Padua, 

 1827. 



t Abhandl. vom kamtheuschen pfauenschw. Helmintholith, p. 48. 



X Annals and Mag. Nat. Hist. 2nd Ser. vol. ii. 1848, p. 258. 



§ Thus described by Loven : " Caput breve latum. Scutum centrale subluna- 

 tum, latum. Sutura pone oculum subrecta, ad angulum ducta, Oculi minuti, 

 arcu infraorbitali elevato, angusto. Thorax articulis (in una specie) duodecim. 

 Terga convexa. Pleurae sulco longitudinali in partem anticam divisae syndesma- 

 lem breviorem, et posticam, majus minusve productam. Pygidium thoraci ex 

 parte conforme, minutum, ex articulis nuraerosis (ex. gr. 16) coalitis, quorum ba- 

 sales aliquot majores, pleuris praediti, reliquis in caudam lanceolatam arctius con- 

 natis."— Ofversigt af Kongl. Vetenskaps-Akad. Forh. 1845, No. 4, p. 110. 



