HARDWICKE'S SCIENCE-GOSSIP. 



>7i 



rows on each side that comprise approximately true 

 hexagons. Z. Woodwardi (Agassiz) occurs in the 

 Norwich (Mammaliferous) Crag of Norfolk, and 

 other species are known from the Swiss Molasse 

 (Miocene). 



above, are merely placed temporarily in the respective 

 positions assigned to them upon somewhat slender 

 evidence, but the relics to be considered in the 

 present section are even less satisfactory in the 

 features they display, and can thus only be relegated 



Fig. 184.— Teeth of Zygohatis. 



Fig. 186. — Spine of 

 Onchus. 



j^V 



Fig. 185. — Outline of Parcxus incurvus. 



Fij. 187.— Spine of Gyro- 

 cantlnts tubcrcu 'atus. 

 (One-third nat. size.) 



ICHTHYODORULITES. 



In conclusion it only remains briefly to treat 

 of a series of Selachian fossils that exhibit no 

 characters sufficiently distinctive to justify their 

 reference to any particular group or family. Many 

 forms, indeed, that have been already mentioned 



Fig. 188.— Oraccinthus Milleri. [After J. W. Davis.) 



to a provisional group until the discovery of more 

 complete specimens reveals their true affinities. 

 These are the detached fin-spines of cartilaginous 

 fishes, frequently met with in a fossil state, and 

 known under the general name of Ichthyodorulites 

 (" fish-spine-stones "). They were first so designated 

 by Buckland and De la Beche, followed by Agassiz, 



