THE BRITISH FOSSIL BRACHIOPODA. 365 



doubtful if the loop of Noiothyris, as he has figured it, is complete ; and, as I cannot 

 help thinking that it is not so, I would not like to place the genus among the Centronellida 

 until this point shall have been satisfactorily settled. 



The genus Leptoccelia, Hall, 1859, type L.flabellites, has always puzzled me; for, as 

 remarked by CEhlert, the distinguished American palaeontologist has classed two very 

 different forms under Leptoccelia. The Leptoccelia of 1857, type L. concava, possesses 

 spirals, and is the type the same author subsequently adopted for his genus Ccelospira. 

 Taking therefore L.flabellites as the type of Leptoccelia, M. CEhlert considers it to bear 

 much affinity to the forms that constitute the genus Centronella. 



I think it will therefore be advisable, at least provisionally, to place Centronella, 

 Leptoccelia, and Bensselaria, in a sub-family following that of the Terebratulida. 



Family— THECIDEIDyE, Gray, 1840. 



Until quite recently the family Tliecideidce was known to comprise the genus 

 Thecidium only, which genus was proposed by Defrance in 1828. It occurs in the 

 Trias, and continues to be represented up to the present time by two species only. 1 Dr. 

 Waagen states, at p. 393 of his work already alluded to, that " In the Alpine Trias, how- 

 ever, there appear at the side of the true Thecidea yet other forms, which have received 

 from Giimbel the name of Pterophloios (' Geogn. Beschr. d. bayr. Alpengeb.,' p. 411, 

 1861). Already Giimbel suspected the Brachiopod nature of these fossils, but it was 

 not before the year 1880 that Zugmayer was in a position to prove their affinity 

 beyond any doubt, and to demonstrate that they were most nearly related to Thecidea, 

 Defr. 2 Zugmayer, however, went too far in this direction, inasmuch as he united 

 Pterop/tloios entirely with Thecidea. Though a certain affinity between the two fossils 

 can certainly not be denied, yet their generic union cannot be advocated. Pterophloios 

 is different in certain very important points from Thecidea. In the large ventral valve 

 the area and pseudo-deltidium are decidedly absent, the cardinal teeth are very little 

 developed, and a long and strong median septum extends from the apex to the anterior 

 margin. Traces of numerous radial septa are also present. In the smaller, dorsal valve 

 the cardinal process is very small ; but otherwise the arrangement of the brachial appa- 

 ratus is very similar to that of Thecidea. It now appears to me that the peculiar struc- 

 ture of the ventral valve is sufficient to distinguish generically between Thecidea and 

 Pterophloios, and that thus the latter genus might very well be retained." 



1 Thecidium Mediterraneum and Th. Barretti. See Davidson " On Recent and Tertiary Species of he 

 Genus Thecidium" ' Geol. Mag.,' 1864. 



2 Thecidea Emmerichi, Giimbel, H. Zugmayer, " Untersuchungen iiber Rhatische Brachiopoden " 

 (' Beitr'age zur Palaontologie Oesterreich-Ungarns '), von E. V. Mojsisovics und Neumayr, Bd. i, p. 19 

 pi. ii, figs. 17—32, 1880. 



