CAMliKIAN B1:ACH1()P()1)A: OP.OLITS AND LINCHILELLA, 

 WITH J)i:SORIPTl()]!? OF NEW SPECIES. 



By CnARL3<:s T). Walcott, 



llo)iof(tni Curator, Dirinioii of Slratif/rapliic I'nlconlolof/y. 



In continuation of the study of the Canibriiin P.rachiopoda all the 

 American forms of Obolus known to me have been considered, and tliose 

 that may be referred to Lint/idella,, which is a somewhat doubtful sub- 

 genus of 0/>f>/».v. A few species from the Lower Ordovician rocks are 

 added, as they form a part of the i)assage fauna between the Cambrian 

 and Ordoviciau faunas. 



OBOLUS Eichwald, 1829. 



(Plate XXVI, ai!;H3-6.) 



Oboliia Eichwald, Zool. Spec, pars, 1829, II, p. 271; and most other writers. — 

 MicKWiTZ, Mem. Acad. Imp. Sciences, St. rt'tcrshoinf;, IS'.W>, «th ser., IV, No. 2, 

 pp. 1-215, pis. i-iii. 



The student is referred to tlie memoir of Mickwit/. for the synonymy, 

 detailed description, and illustration of Obolus and the si)ccies referred 

 to the genus. I have illustrated the interiors of the two valves of (). 

 celatuH and several interiors of O. apoUiiiis from specimens woi'ked out 

 of material kindly sent to me by Dr. F. Schmidt. 



It is stated in the I^aleontology of New York' that Mickwitz did not 

 obtain his results from the type species of the genus Oholns apollinis, 

 but from a hitherto undescribed form, Obolus quvnstedti. I lind that 

 Mickwitz diagnoses the genus and cites Obolus apolUnis as the type 

 (p. l-i8). lie says (p. 24), "A more accurate study of the greatly 

 increased material has convinced me that 0. qtienstedti can not be main- 

 tained as a species, since it is merely the terminal link of a series 

 of variations, which, like var. ma.rimns and ingricvs, can be traced 

 back to 0. apollinis. Thus, the typical species renuiins 0. apolUnis 

 Eichwald." 



The tigures illustrating the new si)ecies are now made uj) as i)lates 

 for a monograph of the U. S. (iieological Survey, and will be transmit- 

 ted for publication probably during 1899. 



' Volume VIII, pi. i, p. 33!). 



Proceedings U. S. National Museum, Vol. XXI— No. 1152. 

 Proc. N. M. vol. xxi 25 385 



