324 Owen — New Genera of Fishes, ^c, 



descript character, he concluded, after careful study and comparison, 

 to be new to Carboniferous Palseontology. 



Professor Owen has proposed for them the following generic and 

 specific appellations : — 



Genus I. — Bittodus, Owen (Strro?, twin or double, 6hov<i, tooth). 



Species 1. — Bittodus parallelus, Owen, 



These teeth have the peculiarity of a double crown, rising from 

 a common base ; the hard dentine of one crown being continued 

 at the side of the base into the corresponding tissue of the other ; 

 thus the two crowns are organically connected together, like the 

 Siamese twins. 



Professor Owen considers it highly probable, from the character of 

 the osseous tissue of the portion of jaw preserved with these twin- 

 teeth, that the genus is referable to the Class of Fishes. 



Species 2. — Bittodus divergens, Owen. 



In this species the two crowns are more divergent from their 

 common base ; they differ in their shape and proportions (being 

 shorter and broader) ; and also in structure. 



Genus 11. — Mitrodus, Owen {jxirpa, mitre, 6hov<i, tooth). 



Species 1. — Mitrodus quadricornis, Owen. 



This tooth sends up four subequal conical crowns from the 

 common osteodentinal base, and its name is derived from its re- 

 semblance to an ancient mitral diadem. 



Genus in. — Ageleodus, Owen {ayikr], crowd or cluster, 6Sov<i, 

 tooth) . 



Species 1. — Ageleodus diadema, Owen. 



In the tooth here described, no fewer than a dozen subequal 

 conical dentinal crowns are developed from a common osteo-dentinal 

 basis. 



Genus IV. — Ganacrodus, Owen {ydvo<;, shine, a/cjoo?, point, o8ou9, 



tooth). 



Species 1. — Ganacrodus hastula, Owen. 



Several of these " enamel-tipped spear-teeth " have been obtained 

 by Mr. Craggs from the shale overlying the " Low Main Seam " of 

 Coal, at West Cramlington. The curious manner in which these 

 teeth are tipped with enamel, at once arrests attention, and the 

 author observes that he had not before met with any sitoilar tooth in 

 the whole range of his odontological researches. 



Genus V. — Ganolodus, Owen {rydvo<;, shine, 0X09, whole, 6Bov<i, 

 tooth) . 



Species 1. — Ganolodus sicula, Owen. 



These teeth offer points of resemblance to the Sauroid type which 

 are wanting in the previous genus; they are amongst the more 

 common forms met with by Mr. Craggs in his prepared coal-sections. 



Genus V. — Mioganodus, Owen {/xelcov, less, ryavo<;, shine, 6Sov<i, 

 tooth). 



Species 1. — Mioganodus laniarius, Owen. 



The section of this tooth resembles an incompletely-formed canine 

 of a young mammalian carnivore, save that the enamel of the crown 

 is not present in mammalian proportions and structure. 



