GADOIDS. 1G3 



in the form of truncated cylinders of various sizes, the largest being 

 most external in the intermaxillary and the reverse in the preman- 

 dibular bones. A group of smaller but similarly shaped cylindrical 

 processes for supporting the teeth are arranged in the form of a chevron 

 across the anterior extremity of the vomer in the cod, after simi- 

 lar maceration. The branchial teeth are more firmly attached, 

 being anchylosed in small groups upon the short obtuse processes 

 of the branchial arches ; there is a double series of these dentigerous 

 tubercles along the concave margin of the second and third arches. 

 The upper and lower pharyngeal bones are beset with small 

 recurved laniary teeth, which are also more firmly fixed than those 

 on the vomer and jaws. 



Retzius compares the dentigerous processes of these bones to 

 epiphyses, but I find that ossification is continued from the supporting 

 bone into them, and have never observed them in a detached state, 

 like the teeth themselves : he correctly describes their texture as 

 being, in the ling, intermediate between that of the bone and tooth. 

 In this species he describes the teeth as being " semi-transparent, with 

 a covering of enamel upon the extreme points of such as are not too 

 much worn. This little covering of enamel is disposed upon the tooth 

 like the shoe of iron upon a spade, being continued from a trans- 

 verse edge forwards and backwards, but being in some produced into 

 a sharp point; the whiteness of the teeth is due to this substance. "(1) 

 The pulp- cavity of the fully-formed tooth in the cod is continuous 

 with the cavity of the supporting osseous cylinder to which it is 

 attached ; it varies in size according to the age of the tooth, and 

 is, at length, reduced to a linear cavity extending along the middle 

 of the axis of the tooth. Processes of the pulp are conveyed by 

 medullary canals which diverge from all parts of the main central 

 cavity into the substance of the dentine ; these are about j^th of an 

 inch in diameter at their origin, but they quickly divide, and their 

 branches form anastomoses with those of the neighbouring tubes ; the 

 loops, thus formed by the smaller terminal branches, constitute a 

 well-defined boundary between the coarse central and the fine 

 external dentine. In this latter layer the calcigerous tubes, which 



(1) Loc. cit. p. 268. 



M 2 



