ZONE OF AMMONITES JURENSIS. 



93 



CONCIIIFERA. 



*Linia bellula, var., Lye. and Mor. 

 *Modiola plicata, Sow. 

 *Perna rngosa, Miinst. 

 *Hinnitcs abjectus, P/til. 

 *Pecten articulatus, Gold/. 

 *Gresslya abdiicta, Phil. 



* — conformiS; Agass. 

 Myaeitcs arenacea, Lye. 



*Homomya crassiiiscula, Lye. 

 *Goniomya angiilifera. Sow. 

 *Myoconcha crassa, Sow. 

 *Cypricardia cordiformis, Desk. 

 *Pecter comatus, GoUlf. 

 Opis carinatns, TT^rigkt. 



* — lunulatus, Sow. 

 Cypricaidia brevis, Wright. 

 Cardium IluUii, Wright. 



— Oppelii, Wright. 

 Cucullaea ferrugiuea. Lye. 



CucuUoca olivscformis, Lye. 

 *Lima clcctra, d'Orb. 

 Unicardiuni, nov. sp. 

 Tancredia, nov. sp. 

 Trigonia Ramsnyii, Wright. 



* — striata, Sow. 



* — costata, Sow. 

 Pecten tc.xtoriiis ? Gold/. 



*Pholadomya fidicula, Sow. 

 — arenacea, Lye. 



Lima ornata, Lys. MS., nov. sp. 

 Astarte lurida, Sow. 



* — excavata. Sow. 



— detrita, Gold/. 



— complanata, Roemer. 



— rugulosa. Lye. 

 Gervillia fornicata, Lye. MS. 



* — Hartmanni, Gold/, 

 Nucula Jurensis, Querist. 



Terebratula subpunctata, Dav. 



Brachiopoda. 



Rhyncbonella cynocepbala, Rich. 

 — Jurensis, Querist, 



The species marked with an asterisk in the above list are found likewise in the Inferior 

 Oolite ; the specimens from the sands, however, are nearly all dwarfed forms, from which 

 it is inferred that the physical conditions which then prevailed were unfavorable to 

 their development. The stunted growth of the stationary Conchifera forms a striking 

 contrast to the size, number and variety of the locomotive Cephalojjoda interred with 

 them in the same bed ; in fact, the dawning existence of these Conchifera aj)pears to have 

 been a struggle for life, whilst the conditions under which the Cephalopoda existed 

 were favorable to their continuance in time, as proved by the number of species and 

 individuals of this class found in the Frocester beds ; their life, notwithstanding, was 

 abruptly brought to a termination by some great physical change which took place about 

 the commencement of the deposition of the oolitic formations. 



