BRACHIOPODA. 9 



" Oryctographie du Gouvernement de Moscou " (1830), is Choristites Mosquensis, 

 Fischer {= Spirife.r Mosquensis, de Verneuil). The generic term was based upon 

 the existence in the jjedicle-valve of highly developed dental plates extending 

 almost or quite to the anterior margin ; a character which has a less prominent 

 development in a few other species, some of which, as for example, Spirifer 

 plicatellus, cannot be satisfactorily grouped with S. Mosquensis on the basis of 

 external characters. The greater or less prolongation of these septa or dental 

 lamellae will be found a feature of comparatively little taxonomic value among 

 these fossils. 



Delthyris, Dalman, 1828.* Dalman divided the genus Spirifek into Del- 

 THYRis and Cyrtia, citing as his first example of the former, Delthyris elevata, 

 Dalman, a species now well known in the European Silurian, and one of the 

 plicate-fimbriate members of the genus. The name Delthyris may, with a 

 restricted interpretation, have a value equivalent to that of Reticularia, McCoy, 

 under which the nonplicate-fimbriate species may be included. 



McCoy, in his " Synop.sis of the Characters of the Carboniferous Fossils of 

 Ireland " (1844), proposed a number of new names to subdivisions of the family 

 DeltbyridjE : 



Fusella {op. cit., p. 132); type, Spirifer fusif or mis, Vh.\\\vps; a small, transverse 

 shell with smooth, rounded ribs, some of which are stated to occur on the me- 

 dian fold. The species is but little known, Davidson statingf that he had seen 

 only the imperfect original in the collections of the British Museum. 



Martinia (op. cit., pp. 128, 139). " Gen. Ch.- — Hinge-line shorter than the 

 width of the shell ; dorsal edges of the cardinal area obtusely rounded ; surface 

 smooth ; spiral appendages small." 



This group is excellently characterized, though McCoy was in error, as shown 

 by Mr. Davidson and the Rev. Mr. Glass, in considering the spirals as having 

 a less development in proportion to the dimensions of the shell than in other 

 Spirifers. De Koninck, Davidson, Waagen and others have observed that the 

 epidermal layer of the shell is minutely punctured. The first species which 



* Kongl. Vetenskaps Akad. Handlingar, pp. 93, 99. 

 t British Carboniferous Brachiopoda, p. .57. 



