72 NEW YORK STATE MUSEUM 



This shell, extraordinarily abundant at some localities, is readily recog- 

 nized by its extremely fine radial surface markings accompanying unusual 

 size. 



Locality. Telos lake dam and Moosehead lake, 7 miles north of 

 Kineo, Me. 



Pterinea radialis Clarke 



Plate 13, figures 10, n, 14; plate 14, figures 1, 3 

 Ste p. 103 



Pterinea radialis Clarke. N. Y. State Mus. Bui. 107. 1907. p. 207 



The specimens of this species from central Maine are rather better 

 preserved than those from Aroostook count}' and also afford series of 

 growth stages which show that younger shells have all the characters of 

 the Chapman sandstone specimens but these are accompanied by shells 

 of larger growth in which the surface radii become somewhat diffuse over 

 the pallial region. Attention is called to the excellent development of the 

 hinge characters as shown in our drawings : in the left valve a multipartite 

 umbonal tooth of 5 to 6 cusps and a strong posterior oblique ridge, both 

 lying beneath a broad striated ligament area.' 



Localities. Matagamon lake, on east side, 1 mile above the dam ; Stair 

 falls, 5 miles below Matagamon lake on east branch of Penobscot river; 

 Cunningham's camp. 



■ Several authors have endeavored t<> ascertain a dependable basis for the subdivision 

 of the old genus Pterinea, but the writer's experience has gradually led to the conviction 

 that Devonic species of what may broadly be termed pterineouis, assume with such ease 

 slight variations in dentition and sculpture that the subsidiary terms already in vogue 

 (e. g. Actinopteria Hall) have an elastic and uncertain value. In practice such terms of 

 restriction are so difficult of use that the best way to avoid the extremes of too broad 

 unification under one generic name and of too narrow subdivision into many seems to be 

 the old method of grouping by approximate species characters. The difficulties in the 

 practical application of such proposed subgeneric or generic divisions of Pterinea are 

 indicated in the series of terms recently proposed by Williams [On the Revision of the Mol- 

 lusk Genus Pterinea Goldfuss. U.S.Nat. Mus. Proc. Apr. 1908. 35:83-90] for the 

 species included within the genus by its founder, Goldfuss. 



The species Pterinea radialis above mentioned was based on examples from 

 the Chapman sandstone; subsequently larger examples of the same type of structure were 

 found in the Moose River sandstone as here mentioned. While it may be that the latter 

 should be regarded a distinct variety, Professor Williams finds, from differences of con- 

 vexitv, that the Chapman shells are of his proposed genus Actinopterella and the Moose 

 River shells of his Follmannella (not Follmannella of Drevermann). In the illustration of 

 the species given by me in Museum bulletin 107, page 207, both forms were shown. The 

 process which resolves one species or at best two very closely allied species into two distinct 

 genera, is difficult of adoption in so impressionable a group as this. 



