DESCBIPTIONS OF SPECIES. 291 



which are also proportionately a trifle broader. In surface ornamentation, shell 

 structure, and internal characters the two forms are wideh' diflferent. 



The preceding remarks are based upon abundant but unsatisfactory material 

 from the Leadville region. There has lately come into my hands a block of chert 

 from Perr}' Park, Colo., upon whose surface numerous specimens of this species 

 occur. They are all internal casts, but present the characters superficial and struc- 

 tural of the Leadville form, although ranging considerably s i aller in size. The 

 lithologic appearance of these fossils from Perry Park is identicall}'^ that of the 

 the Canyon material, and at first sight the little Spirif&rina of the latter localitj^ 

 might be mistaken for the small 8pirife7' of the former. Closer examination, how- 

 ever, shows them to be entirel}' distinct. Even the punctation, traces of which are 

 distinctly preserved upon the cherty casts from Canj^on, are lacking upon those 

 from Perry Park. 



Among the impressions taken at the Larimer County locality are those of two 

 small spiriferoid shells which are believed to belong to this species, although I 

 originally placed them with Spiriferlna solidirostnsf . As the impressions were 

 made from external casts, their generic position is a matter of conjecture. They 

 are of moderate size, with a transverse diameter of about 14 mm. The ventral valve 

 is gibbous and the area appears to be high and incurved. There are six ribs each 

 side of the median sinus, which is somewhat broad and shallow, with a small median 

 plication. In one specimen the surface appears to be smooth, but in the other it is 

 marked bj^ a number of lamellose varices of growth. 



Neither Spirifervna spinosa nor Sp. campestris shows a half-developed rib within 

 the sinus, and, if the impressions belong to Spiriferina at all, this chiiracter would 

 seem to ally them rather with the lamellose section of the genus. There, however, 

 inequalities of growth in the nature of varices are comparative!}' rare, and these 

 impressions also seem to show a shell without lamellose surface ornamentation. They 

 much resemble the form from the San Juan and Crested Butte regions which I iden- 

 tified as Sjnrlferina solUiirostris, but the median rib of the sinus is distinctly stronger, 

 and the surface seems not to have been marked with concentric lamella?. Thej' are 

 also similar to Sp. Tcentuckyensis, but are distinguished by being less sharply plicated, 

 while the sinus is shallower and the median rib more strongly expressed, perhaps, 

 than in that common Coal Measure species. White refers these specimens to Spiri- 

 ferlna octoplicata, which, as identified by him, I believe to be the same as Sp.. cmn- 

 pestrin White. From that species " the impressions differ considerably, being less 

 sharply plicated and having a very distinct rib in the middle of a shallower, broader 

 sinus. 



It is much more likely that the delicate spinose ornamentation of Spirifer sp. h 

 should not have been retained upon the casts or received upon the impressions, than 



a As identified by White at Santa Fe, etc. 



