LOPHIOIDS. 155 



in ordinary mammalian dentine. The tubes divide and subdivide 

 dichotomously four or five times in their progress to the perhiphery ; 

 their diminution of diameter is not proportionate to their degree of 

 subdivision : their diameter at their origin is ^i^th. of an inch ; at their 

 terminations it is ^pooth of an inch : their interspaces equal three or 

 four of their diameters. The small lateral branches given off at the 

 angles or sharp bends of the secondary undulations into the clear 

 uniting substance are unusually conspicuous. A very small propor- 

 tion of the calcigerous tubes proceeds from the apex of the linear 

 pulp-cavity in the axis of that cavity. The apex of the entire and 

 newly-developed tooth is coated with a thin, dense, white layer of an 

 enamel-like substance, which is soon lost. A line of dentinal tissue, 

 more opake than the rest, runs parallel with the pulp-cavity through 

 the dentine about half way between the cavity and the external 

 surface ; this line, analysed with a sufficiently deep powder, is 

 seen to result from an unusual number of lateral branches sent 

 off from a certain extent of the calcigerous tubes along the same 

 parallel line, which branches anastomose together and dilate into 

 small opake cells in the interspaces of the tubes from which they 

 are given off. 



Owing to the extent ofthe secondary inflections of the calcigerous 

 tubes, and the difficulty, if not impossibility of obtaining a section 

 which does not include three or more layers, they exhibit in every 

 part of the tooth the appearance of an universal plexiform inter- 

 weaving ; this character, in combination with their general transverse 

 course and the length of the linear pulp-cavity, might serve to 

 distinguish the tooth of the Lophius from that of a reptile or mammal 

 which it otherwise might most nearly resemble in general form and 

 texture. 



The new or successional teeth are found recumbent in different 

 stages of development, some inclosed in their capsules, others with 

 their apices projecting more or less from the lax gelatinous mucous 

 membrane covering the broad alveolar margin of the jaws. When this 

 membrane is stript off, the successional teeth and their matrices are 

 brought away with it ; their basis being inserted into its substance, 

 just as the quills of the porcupine are attached to the skin. In the 



