342 MR. S. S. BUCKMAN ON BRACHIOPOD MORPHOLOGY. [Aug. I907,. 



compared in their results with that of Eudesia ; but they begin in 

 another way. Magellania flavescens, Terebratula fimbria, T.plicata, 

 and Fimbrioihyris, to name certain notable instances, show a 

 multicostate stage beginning with a full number of costse directly 

 upon a smooth stage. It starts, in old age, as a crinkling of the 

 margin ; and, in series of shells, may be seen extending further 

 and further up the valves (by earlier inheritance), till only a small 

 area of the young shell is left smooth, indicative of the original- 

 smooth lenticular stage. 



With regard to Magellania flavescens, this difference of develop- 

 ment is important, because Hall & Clarke speak of Magellania 

 numismalis, the present Cincta ; but M. flavescens has not come 

 through a Owicto-stage, and shows no sign of the anterior retardation 

 of the Cincta-tjye. What it does show a little indication of is 

 a uniplicate stage, but reversed as compared with Terebratula 

 Whitakeri : that is, it is ventrally, not dorsally plicate. 



Appendix. 



The following emendations of nomenclature are necessary : — 

 Cincta perntjmmus, nom. nov. 



1850. Terebratula numismalis, Davidson (non Valenciermes-Lamarck), Ann. Mag. 



Nat. Hist. ser. 2, vol. v, p. 436 & pi. xiii, fig. 17. 

 1862. Terebratula (Waldheimia) numismalis, Deslongchamps (non Valenciennes) y 



' Pal. franc. : Terr. Jur. Brach.' pi. xiv, fig. 1, p. 83. 



This form differs from Terebratula numismalis, Yal. in being so 

 very much broader, having a much wider apical angle, and in not being 

 more than incipiently truncate until it has reached a much larger 

 size. So a distinguishing appellation is desirable. 



There is a cast of Deslongchamps's figured specimen in the British 

 Museum (Natural History) No. B 16768, and this shows that his 

 side and front views present the shell too thin, with too acute a 

 margin. Davidson's delineations were from this same specimen of 

 the Deslongchamps Collection ; and his side view is the more 

 correct. 



Trigonellina, gen. nov. 



Type: Terebratula pectunculus (Schlotheim) (Quenstedt). 



Shell-ornament multicarinate, opposite. Loop muehlfeldtiform. 



Distinguished from Muehlfeldtia, Bayle = Megerlia, King, by the 

 multicarination, an angular hinge-line, and a somewhat differently- 

 disposed loop ; from Ismenia, King, by the carination being opposite 

 and not alternate ; from Trigonella, Quenstedt, by being in a 

 higher state of costation, but having a lower-stage loop. 



King, ' Perm. Foss.' (Pal. Soc. Monogr. vol. iii) 1850, cited Tere- 

 bratula pectunculus as type of his Ismenia ; but this was evidently 

 a lapse for T. pectunculoides, as is shown in his p. 245. 



The want of a satisfactory generic name under which to range 

 these Jurassic shells makes it desirable to give the present 

 denomination. 



