98 University Geological Survey of Kansas. 



SPIRIFER. 



Sowerby, Min. Con., II, p. 41 (1815). 



Hall and Clarke, Pal. N. Y., VIII, pt. II, pp. 1-40, (1893) ; etc. 



Billings, Can. Jour., VI, p. 253, (1861) ; etc. 



This genus is very grealty developed in the Paleozoic rocks of 

 America, though there are but two forms that have been recog- 

 nized with certainty in our Coal Measures. Hall ( loc. cit.) di- 

 vides the genus into six groups, as follows : 



I. Radiati. " Smooth, radially undulated or plicated; fold 

 and sinus smooth ; entire surface covered with fine, filiform ra- 

 diating stria* which may be minutely crenulated or granulose." 



II. Lamellosi. " Radially plicated ; surface covered with nu- 

 merous concentric lamellae. In Silurian species the fold and 

 sinus are non-plicate ; the later forms usually bear a low median 

 depression on the fold accompanied by a corresponding median 

 ridge in the sinus." He further divides this group into two 

 smaller ones — the Septati, those possessing a mesial septum in 

 the pedicle valve, and the Aseptati, without this septum. 



III. Fimbriati. " Shells with a few low plications or none ; 

 hinge line not greatly extended, often shorter than the greatest 

 diameter of the shell ; dental lamella? moderately, sometimes 

 notably, developed ; a low median septum may exist in the 

 pedicle valve. Surface covered with concentric rows or fringes 

 of fine spines." He also divides this group into two smaller 

 groups — the Vnicispinci, those species in which the concentric 

 fimbria? are made up of short, simple, hollow spines (Delthyris 

 Dolman) , and the Duplicispiriei, those with larger, compound, 

 hollow spines (Reticularia McCoy) . 



IV. Aperturati. Those having plications on the fold and 

 sinus. These are the typical Spirifers. They are divided into 

 several smaller sub-groups which are of little interest here. 



V. Ostiolati. Median fold and sinus without plications. 



VI. Glaberati. Surface smooth ; fold and sinus faintly devel- 

 oped. These he divides into two smaller groups, the Aseptati 

 and the Septati, according to the presence or absence of the 

 dental lamella? and mesial septa. These are equal to Martinea 

 of McCoy, Mdrtinopsis Waagen, and Mentzelia Quenstedt. 



