6 



ME. E. T. NEWT0K ON THE OCCEEEEXCE OF [Feb. I904, 



few of the lower denticles are at right angles with the rest of the 

 crown. In the British specimen, on the other hand, the lower 

 edge of the enamel is strongly bent, while the lower denticulated 

 margin is only slightly curved at its lower end. There is likewise 

 a difference in the denticles ; the Russian specimen having them, as 

 in Edestus minor, double and not triple. 



Dr. Karpinski was evidently in some doubt as to his specimen 

 being really an example of E. minor, for he says that it is either 

 this or a closely-allied species, and I am inclined to think that the 

 latter suggestion is the more justifiable. But, however that may 

 be, the Smallthorne specimen can scarcely be referred to Edestus 

 minor, the differences mentioned above preventing such a reference. 

 Bearing in mind, therefore, the most striking peculiarity of our 

 fossil, I propose to name it Edestus triserratus. 



Pig. 2. — Segments of Edestus triserratus restored. (4 nat. size.) 



A = Anterior, oldest segment. B = Posterior, newest segment. 



Fortunately the basal portion of our specimen and its trough are 

 so well shown, that the manner in which the segments fitted 

 together is obvious ; and, taking advantage of this, the appearance 

 of half a dozen such segments combined is shown in text-fig. 2. 



The crowns of all the teeth in Xewberry's figure of E. minor are 

 so nearly of the same size, that one is justified in assuming that 

 the teeth and segments of our British specimens did not vary greatly 

 in this respect, and consequently the combined series would have 

 had much the appearance of my restoration ; but probably the 

 basal portions of the older segments of Edestus changed somewhat 

 in shape by continued deposition or absorption of bony material. 

 At first sight it is not clear which is the growing end of such 

 a series. Among a large number of segments of E. Heinrichsii 

 that Newberry had for examination was one which possessed no 

 groove ; and he concluded that this was the first of a series, 

 that a new segment was formed with its base under the toothed 



