2ii 



Description. — The table of syuonyms prefixed to this article is very 

 limited when compared with the lists given in the works of M. d'ORBiGNY 

 and Professor Haukk; it is due, therefore, to the reader and myself 

 that I should give my reasons for excluding many of the citations of my 

 contemporaries. In my description of Ammonites Bucklandi, Sow.,'*' I 

 have stated that M. Bruguiere, in the Encyclopedic Methodique, torn. 

 1, p. 39, desciibed, under the name of Ammonites bisulcata, two distinct 

 forms. — (A.) Ammonites Bucklandi, Sow., and (B.) Ainmonites multi- 

 costata, Sow. These two forms were thus described: — 



A. — '^^ Ammonites costis simjilicibv^ raris, dorso bisulcata, carina acuta 

 intermedia." 



B. — "Ammonis comu spina in ambitii eminente, striis lateralibus, ex 

 toto orbem extimum trajicientibus." 



The variety A. had been previously figured by Martin Lister in his 

 Conchyl. Angli£e,p. 207, tab. 6, fig. 3, and by Lang in his Historia Lapidum 

 Figuratoiiim Helvetia, tab. 24, fig. 1, and there described as "Am,monis 

 cornu striatum vulde striis integris elatis in spinam inter duos sulcos 

 eminentum abeuntibiis." The variety B. had been included in Britguiere's 

 general diagnosis of Ammonites bisulcata, and most authors have followed 

 Bruguiere in grouping both forms under one specific name. I am inclined 

 however, to think that Sowerby was right when he figured both forms 

 under distinct names, as M. d'ORBiGNY and Professor Hauer, in their 

 works already cited, have figured good type forms of A. multicostata, Sow. 

 I assume that this is the recognized type of Bruguiere's A. bisulcata in 

 France and Germany, whereas the true A. Bucklandi, Sow., is seldom 

 figured in any woi'k on Lower Lias fossils. I have, therefore, determined 

 to retain Bruguiere's name for his var. B., and Sowerby's name for 

 var. A. In accordance with this view I have excluded all references 

 to the synonyms of authors, unless I had a figure or a specimen for my 

 guide, to determine the form referred to in the citation ; this mode of 

 proceeding has necessai-ily diminished my list, but makes it more correct 

 for reference. Am,monites bisulcatus has a depressed discoidal shell, 

 with a strongly tricarinated back, and subquadrate whoi-ls. The sides are 

 provided with 30 to 40 simple, narrow, slightly bent ribs, each terminating 

 in a blunt tubercle, near the dor.sal border. From the tubercle the rib 

 bends shai-ply forwards, and disappears at the outer carinse. The back is 

 flat and tricarinated, the median keel a little more prominent than the 

 laterals, and the two sulci, although well marked, are not very dee\i in 

 my specimens ; the lateral carinae are well defined ; the shell is bevelled 



* Proceedings of the Cotteswold Naturalists' Club for 1863, p. 173. 



