322 SxsTEHATic Paleontology — Middle Devonian 



in mature specimens they are ten or twelve mm. distant from each other, 

 and in the extremely large specimens more than fifteen mm. distant ; their 

 concavity greater tliaii the deptli of the air-chambers; siphuiicle is well 

 defined at the septa, close to the ventral side, and distinctly circular in 

 section. Test one to two mm. thick on the outer chamber of older indi- 

 viduals, and about half as thick in the smaller ones ; the surface marked 

 by strong, lamellose, curving striae, which in the young shells are crowded 

 into fascicles, rising into ridges, and these curving annulations are some- 

 times indicated, on the cast of the living-chamber of the young shell, by 

 low undulations. The striae, on the lateral faces, make a curvature very 

 nearly corresponding to the curvature of the septa ; and in the young shells 

 they make an abrupt retral curve over the low saddle, thence to the 

 middle of the periphery, where they are recurved, forming a deep sinus 

 upon the ventrum ; the place of the saddle is indicated by a double revolv- 

 ing groove, margined on each side by a low carina, and separated by a 

 stronger similar one ; as the shell enlarges, the lateral of these two grooves 

 first becomes obsolete, and finally also the other, leaving a simple obtuse 

 angle along the line of the saddle, over which the striae in their retral 

 curve are more conspicuous. The individuals of this species present a 

 great range in size and proportions ; the smaller specimens do not exceed 

 thirty mm. in their greatest dimensions, while many specimens have a 

 gi'eatest diameter of 150 to 200 mm. and one specimen has a diameter 

 of over 300 mm. 



Fragments of a fairly large specimen were obtained in the lime- 

 stone lentil in the West "Virginia Central Eailroad cut at 21st Bridge, 

 which are mostly smooth internal impressions and are scarcely well 

 enough preserved for illustration. One fragment shows the inside of 

 the shell and where it is exfoliated curving striae similar to those 

 represented in figures of medium sized specimens of this species. The 

 best specimens were shown Dr. J. M. Clarke who identified them as 

 Agoniatites expansvs (Vanuxem) and later in commenting upon a speci- 

 men of Badrltes aciculatus (Hall) embedded in a portion of the limestone 

 which also contained a fragment of this shell he wrote : " Of additional 

 interest to me is the fragment of large Goniatite on the reverse of this 



