PISCES 



87 



No. 397. G-yrodus umbilicus, Agass. 



Palatal Teeth, on slab. From the same locality and Museum. 



Price, $0.75. 

 No. 328. MegalurTlS lepidotUS, Agass. 



Skeleton, on slab. This genus of homocercal Ganoids is distinguished by 

 a large head with jaws armed with large and small teeth intermingled and by a 

 large, round tail. The scales resemble those of the Carp. This complete skele- 

 ton was found in the Lithographic slate (Upper Oolite) of Solenhofen, Bavaria, 

 and is in the Museum of the University of Munich. Size, 17 x 8. Price, $2.50. 



No. 329. Megalurus elegantissirrms, Wagn. 



Skeleton, on slab. This small Ganoid Fish, with largely expanded, homo- 

 cercal tail, is from the same locality and Museum as the preceding. 



Size 8x5. Price, $1.00. 



Order 2 — Placoids. 



The Placoids (or Selachians as they are now more generally termed) 

 have a purely cartilaginous skeleton and a rough skin, often composed 

 of rhombic or angular plates, each rising into a point at the centre. 

 The teeth are confined to the maxillary and mandibular bones. This 

 Order Agassiz in his " Contributions " elevates to a Class. 



The Placoids, being Cartilaginous, have left little behind save 

 spines, teeth, and a few scales. The fossil spines are called Iclithyo- 

 dondites, and abound in the Secondary deposits. Agassiz enumerates 

 in his " Poissons Fossiles " about 70 species. Of extinct Placoids, 2 

 are known to be Silurian, 7 Devonian, 82 Carboniferous, 38 Permian, 25 

 Lias, 60 Oolite, 52 Chalk, and 86 Tertiary. The Cestracionts began in 

 the Lower Devonian, and culminated in the Trias. The Squalodonts or 

 True Sharks, began in the Jurassic and culminated in the Miocene. 

 The Hybodonts began in the Trias and culminated in the Jurassic. The 

 Rays appeared first in the Carboniferous and the Cliimseroids in the 

 Oolite. 



No. 330. Squatina acanthoderma, Fraas. 

 Body and Head, on slab. This extinct Placoid 

 approached the Pay family, by the situation of the 

 eyes on the dorsal face and by the development of 

 the pectoral fins. The mouth was at the end of 

 the muzzle. The contour and outer border of the 

 body has left a full impression on the stone. This 

 fine fossil was discovered in the Lithographic slate 

 (Upper Oolite) at Eichstadt, Bavaria, and is in the 

 Tylerian Museum at Haarlem, Holland. 



Size, 2 ft. 5 in. x 1 ft. 8 in. Price, $7.00. 



