248 THE VOYAGE OF H.M.S. CHALLENGER. 



The parapophyses of the abdominal vertebrae are short, placed on each side of the 

 lower surface of the vertebrae, thus enlarging the abdominal surface of the column. 

 They are lengthened on the first three or four caudal vertebrae, and then those of each 

 vertebra coalesce at their distal extremities, forming a wide haemal canal which 

 disappears in the posterior fifth of the length of the tail. The interhaemals of the 

 anal spines are strong, corresponding in length to the exterior spines ; only the anterior 

 are somewhat dilated, the remainder being rod-shaped, and graduallj^ passing into the 

 interhaemals of the anal rays ; with regard to the numbers, the interhaemals correspond 

 to the anal rays, and the haemals nearly to the interhaemals. 



A short separate bone is horizontally intercalated between the distal extremities 

 of every two interhaemal spines, each taking part in the articulation of an anal spine. 



Ribs begin to be developed on the fourth vertebra, being inserted immediately 

 below the neural arch ; they are extremely slender, and become gradually longer on the 

 posterior abdominal vertebrae where each coalesces with a floating rib, the ribs thus 

 having the appearance of consisting of two roots (one being fixed to the vertebra and 

 the other free), and of a simple distal portion. Of the caudal vertebrae only the 

 anterior possess ribs. 



The pubic is a simple feeble bone, with a transversely swollen, cartilaginous base 

 for the articulation of the ventral rays ; it is a thin lamella tapering in a fine point in 

 front, and with a lamellar longitudinal ridge at its ventral surface. 



Notacanthus nasus. . f(V<^ 



Notacanthus nasus, Blocb, Fisch., vol. xii. p. 113, tab. 431. > ^a^/ 



„ „ Cuvier, vol. viii. p. 467, pi. ccxli. \^*' 



„ „ Gairaard, Voy. Isl. et Gronl. Zool. Poiss., pi. xi. '' 



„ „ Littken, Vid. Meddel. nat. Foren. Kj0benlia7n, 1878, p. 145. 



B. 8 (9?). D. 9-10. A. 13-17 I 116 (ca.). P. 14-16. V. 3 | 6-7. 



Gill-openings reaching forwards to below the posterior margin of the orbit. 

 Intermaxillary teeth compressed with the point directed outwards, forty on each side ; 

 the mandibulary and palatine teeth smaller, more erect, and anteriorly in a double or 

 triple series. Ventral fins scarcely united {vix conjunctse, Llitken). 



Only a few specimens are known from the deep-sea off the coasts of Southern 

 Greenland and Iceland.-^ 



1 In the absence of all information as regards the dentition, and even of the size of the specimen, it is impossible to 

 form an opinion as to the distinctness of a Notacanthus obtained by the U.S. Fish Commission in the Gulf Stream 

 (lat. 40°) in 547 fathoms. It is characterised thus : — Notacanthus analis, Gill {Proc. U.S. Nat. Mus., vol. vi., 1884, p. 255) : 

 D. 11 I 1. A. 18 I 1 " The length of the snout and diameter of the orbit subequal, and greater than the interorbital 

 area, and the snout projecting about one-third of its own length beyond the mouth." 



IVA. 



7 



