8. S. Buchnan — On Jurassic Ammonites. Ill 



Sonn. BiicTcmani, n. sp., an allied form, for which I tender my thanks — 

 " S. deltafalcata, Quenstedt," — and Witcliellia jpimctatissima, n. sp. 



Plate X. illustrates S. alsatica, Haug, now figured for the first 

 time — a small S. deltafalcata which possesses connate ribs, and is 

 thus different from those in pi. ix — " WitchelUa complanata " and 

 " W. liostraca, Buckm.," with the specific determination of which 

 I agree, but which I placed in my genus Dorsetensia — " WitchelUa 

 regrediens," — " W. Edouardiana," — " W. crassicarinata" which 

 looks dangerously like what I should expect to be the young of 

 my Dorsetensia tecta, — " Harpoceras capillatum, Denckmann," — and 

 " H. cf. aalense," an interesting species from the " Concavum-zone," 

 which has ribs far too falciform for close connection with aalensis. 



My genus Dorsetensia Dr. Haug has rejected : he merges it in 

 WitchelUa, on the ground that WitchelUa only differs from Dorset- 

 ensia by the persistence, in adults, of two furrows, one each side of 

 the carina. This difference, he contends, is not sutficient for a genus, 

 or even for a sub-genus ; but with this dictum I venture to 

 disagree : in my opinion any one character common to several 

 species is of generic importance, provided it be not the result of 

 homoplasy. 



1 fear that a certain misunderstanding of my genus WitchelUa is 

 answerable for Haug's rejection of Dorsetensia : the author could 

 not find " lateral tubercles " in any WitchelUa. Now, soon after 

 founding my genus, I wrote that some specimens showed sharp 

 spines in the inner whorls.^ The phrase "sharp spines" is stronger 

 than "lateral tubercles"; and in face of this distinct assertion the 

 author's remarks appear a little rash. The question which occurs 

 to my mind is : Do any of the specimens which he possesses belong 

 to my genus WitchelUa as I should define it ? On this point 1 think 

 there may reasonably be some doubt; because the only species which 

 I recognize as having any likeness to WitchelUa is his fig. 3, pi. viii. ; 

 but this the author calls " Sonninia." 



Dr. Haug says that my Dorsetensia pidchra is d'Orbigny's 

 Edouardia7ia, and my Edouardiana he names afresh, "regrediens." 

 I am willing to admit that, Edouardiana being a French species, the 

 author ought to know more about it than I do ; but, if he be correct 

 in these statements, d'Orbigny's must be a very unfortunate drawing. 

 My pulchra is practically smooth half-a-whorl sooner than the 

 specimen shown in d'Orbigny's figure of Edouardiana ; while, 

 further, my pidchra shows in its septation the very character— a 

 two- instead of a three-pointed superior lateral lobe— which Haug 

 calls attention to in his regrediens as a distinction from Edouardiana. 



Among the many points of interest in this work I notice one 

 thing with satisfaction, namely, that Dr. Haug now agrees with my 

 view as to the position of WitchelUa:^ he places it as " un genre 

 voisin du genre Sonninia." Formerly he regarded the species now 

 known as WitchelUa {-\- Dorsetensia, etc.) as allied to Gramrnoceras ;^ 



' Descent of Sonninia, etc. Q.J.G.S. vol. xlv. p. 658. 



2 Ibid. p. 658. 



^ Beitrage Monogr. Saj-poceras, Neues Jahrbuch fiir Mineral, etc. 1885. Beil- 

 Bd. iii. p. 637. 



