ZOOLOGY. 791 



it presents above a mesial ridge continuous with the spinous processes 

 and at the sides ridges continuous with the line of the transverse proc- 

 esses. The plane of the occipital region is vertical or inclined from 

 below upwards and backwards. There is no lateral occipito- vertebral 

 articulation. The principal vagus foramen is placed far from the fora- 

 men magnum ; the lower roots of the nerve pass out by from three to 

 five distinct canals which are in the line with the foramina for the spi- 

 nal nerves. The vestibulum forms a distinct eminence on the surface 

 of the infero-i3lateral portion of the auditory region. The articular sur- 

 face for the hyo-maudibular is simple, and not sharply marked oft' from 

 surrounding parts. The post-orbital process presents an articular sur- 

 face for the palatoquadrate. The orbit has no cartilaginous floor. 

 There is an ethmoidal canal. There is no tri-radiate rostrum. Eepre- 

 senting the ant-orbital cartilage of rays is an ant-orbital process. There 

 are either six or seven branchial arches; the external arches are incom- 

 plete. There is only one dorsal fin ; its rays are supported by a broad 

 basal cartilage." . 



In the Neoselachii " the centra of the vertebrae are well ossified. The 

 occipital region is well marked off from the vertebral column. The plane 

 of the foramen magnum is vertical or slopes forwards. The principal 

 vagus foramen is usually approximated to the foramen magnum, and 

 there is never a row of accessory foramina in line with the foramina of 

 spinal nerves. There is no distinct elevation on the surface of the skull 

 marking the position of the vestibule. The articular surface for the 

 hyo-mandibular is complex. The post-orbital process never presents 

 an articular surface for the palatoquadrate. The orbit has a cartila- 

 ginous floor. There is no process representing the ant-orbital cartilage 

 of the rays. There are never more than five branchial arches. There 

 are two dorsal fins, which may or may not present broad basal carti- 

 lages." 



The suborder Palseoselachii is represented by only one family, the 

 JSTotidanidae, while the Neoselachii examined by Professor Haswell are 

 differentiated by him into the families Cestraciontidse, Lamnidae, Scyl- 

 liolamiiidse, Scyllidse, Ehinidae, and Pristiophoridse. 



Fishes or Teleostomes. 



Pterospis and Scaphaspis. — In a Devonian bed in Galacian Podolia 

 (Eussian-Poland) were found two shields, one a Pterospis and the other 

 a Scapbaspis united, and universily opposite each, and giving the im- 

 pression that they were in natural union ; the Pterospis, however, pro- 

 jected further forwards than the Sca^jbaspis. It has therefore been 

 urged by Dr. A. Altb that the Pterotpis was the dorsal and the Seaphas- 

 pis the inferior buckler of the same fish. The mouth is thought to 

 have been in the inter-space between the two shields and thus to have 

 been somewhat inferior. {Abhandl. Sitz. Ber. Alad. Krahan, v. 11, pp. 

 160-187, pi. 6, Archives Slaves de Biol., v. 1.) 



