NOTES ON THE CAMBRIDGE GREENSAND. 491 



There is another form, however, with which they have some 

 relations, viz. A. sexangulcitus, Seeley. To the figured type of 

 this they have little resemblance ; but other specimens which 

 Mr. Seeley has recently referred to this species are very like them, 

 and, if he is not mistaken in these later determinations, I think the 

 above name must also be added to the synonymy of A. rliamno- 

 notus. It is possible that the two originally described specimens 

 may really be a distinct species ; but I am more inclined to consider 

 that these constitute a strongly marked variety of this variable form, 

 for which the varietal designation sexangulatus may be conveniently 

 retained. 



In thus proposing to group under one specific name several forms 

 which, in their extreme modifications, are very unlike one another, 

 I am ouly following the plan suggested by Mr. Seeley himself in 

 his excellent paper on the Cambridge Ammonites, in which he 

 describes numerous varieties of the four types, splendens, auritus, 

 Raulinianus, and Studeri, regarding these as but subspecies of a 

 larger group, for which he suggests the name of A. permutatus. 



Ammonites ccelonotus, Seeley. 



A. coelonotus, var., Seelev, Ann. & Mag. Nat. Hist. 3rd ser. 

 vol. xvi. p. 238, pi. x. fig. 3. 



A. valbonnensis, Hebert & Mun.-Ch. in Description du Bassin 

 d'Uchaux, Ann. des Sc. Geol. tome vi. pi. 4. fig. 3. 



It may be well to call attention to the identity of these two shells, 

 separately figured and described in the two publications above 

 mentioned. Mr. Seeley describes two varieties of his species ; but the 

 figures are unfortunately very poor. They are, however, sufficiently 

 recognizable ; and had Prof. Hebert seen them, he would probably 

 not have described his A. valbonnensis as a new species. One 

 advantage, however, has been derived from his oversight, namely 

 the presence of an excellent figure of this variety in the Annales des 

 Sciences Geologiques ; it might almost, indeed, have been taken from 

 a specimen now in the Woodwardian Museum. I would suggest, 

 therefore, that it hereafter stand under the name of A. coelonotus 

 var. valbonnensis. 



Ammonites acanthonotus, Seeley. 



A. acanthonotus, Seeley, Ann. & Mag. Nat. Hist. 3rd ser. vol. xvi. 

 p. 234, pi. xi. fig. 5. 



After describing this peculiar form, Mr. Seeley remarks that a 

 slight inflation extends all round one side of the whorl ; " but," he 

 says, " from the near resemblance the shell has to A. glossonotus, 

 I am not inclined to give that weight to the distortion it other- 

 wise would have. The late Dr. S. P. Woodward, in 1862, regarded 

 this shell as a monstrosity of A. lautus, Sow., a view with which 

 I cannot agree." 



In my opinion, however, there can be no doubt that Dr. Wood- 



