398 CARKONIFKKOUS FORMATIONS AND FAUNAS OF COLORADO. 



aro evidontl}^ rcliitcd to tho punctate structure of tho sholl, each of tlio spiiiulos 

 reprcsentiiio- a pore. "\Miotlicr they are merely the tiny plugs of calcite which 

 tilled the perforations in the shell, the latter having been worn from about them, 

 or whether the shell projected around each aperture in the shape of a minute 

 tube, 1 have not been able to assure myself, but I am inclined to the latter opinion. , 

 The differences just pointed out are so striking and in the main so unifoi'm that 

 at fii'st I was for recognizing the shells which were characterized by them as 

 distinct species. Later, associated with shells of the first type were found a 

 number of individuals intermediate between it and the other, and continued search 

 resulted in finding on some specimens of Spiriferina »2?iri<)Ka, a species in the 

 closest degree related to that under discussion, both kinds of surface developed 

 in patches upon the same valve, the one condition clearly resulting from the other 

 by a process of erosion. I think, therefore, that there is no room for doubt that 

 the apjjearances described are conditioned entirely bj^ preserA'ation. The inter- 

 mediate style of markings mentioned consisted of a surface thicklj^ covered with 

 line spinules, among which at intervals were distributed larger ones of the usual 

 size, the impunctate, striated, outer layer having been removed without destroj'ing 

 the larger spines. Often when the shell is silicified the outer layer is missing 

 and the coarselj' punctate structure is brought prominentl}- to view. The shell 

 then has a reticulated, almost spong}^ appearance. This is the condition of the 

 type specimen of Spiriferina gonionotiis. The specimen from Camp Cottonwood 

 figured by White as Sjp. octoplicata and the other material from the same locality 

 resemble Meek's tj^pe very closely. These specimens are not silicified but exfoli- 

 ated, showing only the strongly punctate shell structure. The other specimen 

 figured by White is from Santa Fe, N. Mex. It and the rest of our Santa Fe 

 material shows only the minute, closely set spinules. The specimen figured by Wal- 

 cott was collected from the Pancake Mountains, north end of Coal Hill, White Pine 

 County, Nev. It is silicified and shows the large spines and, indistinctly, the 

 coarsely punctate shell structure. Other specimens from Coal Hill have the surface 

 better preserved, but in the matter of shape are less perfect. Some of them show 

 the lai'ge spinules, impunctate outer layer, and fine concentric markings above 

 referred to, and others are intermediate between the two main tj'pes of preservation 

 which I have been able to distinguish, having the large spines of the one distributed 

 among the fine spinules of the other. My Colorado material is also exfoliated, but 

 belongs with little doubt to this division of the genus. The type specimen of Sp). 

 gonionotus is somewhat peculiar in its shape, and differs from the rest of the mate- 

 rial by some of the same characters by which Meek sought to distinguish it from 

 Sj>- hentuckyensis and 8-p. octoplicata. These are chiefly its highly inflated valves 

 and prominent fold, which, projecting in front, gives to the outline a rather mark- 



