37iS Oeological Society. 



North Staffordshire ; but it does not appear to be desirable to con- 

 clude that the horizons are identical, until further evidence of faunal 

 development has been obtained from the Bristol area. The brachio- 

 pod-fauna contains forms identical with, or closely approximating 

 tx), species occurring in the Cyatliaxonia- and Dihimophyllum- 

 Zones. 



The palffiontological description contains an account of the different 

 species collected, including notes on Prochictus, OJionctcs, Derhya, 

 and Ofthothetes, contributed by Dr. A. Yaughan, and new species of 

 Choneies, Raphistoma, and Loxonema. 



2. ' Brachiopod Morphology : Cincta, Eudesia, and the Develop- 

 ment of llibs.' By S. S, Buckman, F.G.S. 



The test-ornament of brachiopods is found in three main phases : 

 smooth, ribbed, and spinous ; and of these three, a costate 

 species is more advanced than a smooth one, and less advanced 

 than a spinose one. There are catagenetic developments, also, 

 in reverse order; biit these may, for the present, be neglected. 

 Dall has stated that Cincta (Terehratula-numismalis Group) is a 

 synonym of Eudesia {T.-cardium Group) ; but, although it would be 

 quite possible for costate forms to be developed from the smooth 

 Cincta, yet they would not be costate forms of the Eudesia-ijT^Q : 

 in the Cmc^a-type the costse developed would be of the kind 

 which produced opposite carinatiou of both valves, while in 

 Eudesia the costae on the two valves are alternate, the carina 

 of one valve being opposed by sulci in the other. This fundamental 

 difference not only prevents the inclusion of Eudesia and Cincta in 

 one genus, but shows that they belong to entirely different series. 

 The first phase of development dealt with may be called the 

 lenticular stage, which might develop in either of the two 

 directions indicated. The next phase would be the Cincta-sidige, 

 in which the front margin is rounded in youth, truncate in 

 adolescence, incipiently excavate and bilobate in the adult, as the 

 growth-lines of the specimens show. The Cinc^a-stage may develop 

 in two directions — out of broad forms the quadrifid stage, out of 

 narrow forms the cornute stage. The next development may be 

 called the quadricarinate or trigonellid stage; and the fourth 

 stage, the multicarinate or pectunculus-?>tai^Q. In Eudesia 

 there is a highly-developed multicarinate stage, but the carinae are 

 alternate, not opposite. In degree of ribbing it is higher than 

 Cincta, and in a way even higher than the pectunculus-?,i2igQi ; but 

 both the ribbing and the loop forbid connexion with Cincta. The 

 preceding stage is exemplified by Ismenia pectunculoides. A prior 

 stage may be seen in Megerlia Munieri ; and, as an example of 

 the incipient uniplicate stage, Terehratida WMtalceri may be given. 

 Certain emendations in nomenclature appear to be necessitated as 

 a result of this communication ; new names are given, and their 

 application defined. A Table is added to show the successive stages 

 of development along the two lines. 



