BRACHIOPODA. 263 



radiating surface striae of the latter shells. In Amphigenia the high dental 

 lamellae bounding the muscular impressions of the pedicle-valve are supported 

 by a median septum ; in RENSSELiERiA and Megalanteris this supporting septum 

 is wanting, the convergent lamellge resting on the bottom of the valve. In 

 Newberria, however, these lamellae are exceedingly divergent and quite short ; 

 the muscular impressions being sunk in the shell without other delimitation. 

 In typical forms of Renssel^ria, as well as of Amphigenia, the hinge-plate is 

 not deeply divided medially, and is perforated by a visceral foramen, though the 

 latter is frequently closed. In Newberria there is no evidence of this perfora- 

 tion. The peculiar apical structure of the hinge-plate has been made out from 

 internal casts of the best known species, N. Claypolii, Hall, and, upon com- 

 paring with these the description and figures of Megalanteris inornata {Atrypa 

 inornata, d'Orbigny), given by CEhlert,* the latter clearly evince a similar 

 structure. The strong development of the sinuses in Newberria is a feature 

 of distinction. In the allied genera Renssel^ria, Amphigenia and Megalan- 

 teris, the sinuses are more or less clearly defined in the umbonal region and 

 about the area of muscular insertion, but in Newberria the great trunk vessels 

 originate about the ante-lateral edges of the muscles and traverse the brachial 

 region, while the posterior surfaces of the valves are free of them. 



The distinctive differences in this type of structure from Renssel^ria were 

 indicated in the Fourth Volume of the Palaeontology of New York, where the 

 species there described as Rensselizria ? Johannis was referred to that genus with 

 doubt and a suggestion incidentally made that a new generic division might, 

 with further knowledge, be erected for it.f This fossil was from the beds of 

 the Hamilton group, at Waterloo, Iowa. There was also known at that time, 

 in the collections of Professor G. C. Swallow, then State Geologist of Missouri, 

 a larger form possessing similar characteristics, from the Hamilton rocks of 

 Moniteau county, Missouri, which has since been described as Newberria Missouri- 

 ensis, (Swallow) Hall.J 



* Annales des Sciences Geologiques, vol. xix, art. No. 1, p. 20, jil. ii, figs. 1-10. 



t The term Rensselandia was there used in this incidental manner, but as it was not defined and 

 etymologically is without meaning, it can not be adopted. 



t Tenth Report of the New York State Geologist, p. 97, pi. v, figs. 10-12. 1891. 



