Conchifera. 237 Yoldia. 



YOLDIA, Miill. 1832. 



Evansi, M. & H. (Nucula), 1860, Proc. Acad. 429. Neb. C 



scitula, M. & H. " id. 428. Neb. C. 



subnasuta, H. & M. Sp. (Nucula), M. & H. id. 429. Neb. C. 



ventricosa, H. & M. Sp. " M. & H. id. 429. Neb. C. 



HIPPURITINAE.* 



Batholites, Montf. 1808 (HIPPURITES, Lam. 1801). 

 organimns, Montf. (Hippurites), Conch. Syst. 1, p. 334. 



BIRADIOLITES, d'Orb. 1847. 



angulosa, d'Orb. P. F. 233, 574, 7-11. Fr. C. 



canaliculata, d'Orb. P. F. 230, 572. Fr. C. 

 cornu-pastoris, Desm. Sp. (Hippurites), d'Orb. P. F. 231, 572. 



Fr. C 



fissicosta, d'Orb. P. F. 234, 575. Fr. , C, 



quadrata, d'Orb. P. F. 232, 574, 1-6. Fr. 0, 



* After a careful study of all the material at my disposal, and after reading the 

 views of the numerous able students who have studied the subject, I have been 

 led to believe that this curious group of genera, constituting according to some 

 authors a distinct order, according to others, a suborder, and considered by still 

 a third class, as only a family, are more nearly related to the Conchifera than to 

 the Brachiopoda. From their paradoxical nature, they have been considered Ce- 

 phalapoda, Zoophytes, Brachiopoda, and as a totally distinct order. 



Mr. Woodward, in a very able paper in the tenth volume of the Quarterly Jour- 

 nal of the Geological Society of London, points out their true character, refers 

 them to the Conchifera, and considers them a family, related to the Chamacea 

 and Cardiadae. I am inclined to consider them rather as a suborder of the Co7i- 

 chifera. 



The reasons given by Woodward for separating them from the Brachiopoda^ 

 and uniting them with the Conchifera, are as follows : 



"1. The shell is composed of three layers, which is not the case in any Bra- 

 chiopod. 



"2. The prismatic-cellular structure is like that of Penia and Aetheria, and 

 not like any Brachiopod. 



