356 L. F. Spath — Jurassic Aonvioiiites from East Africa. 



1866 A. tripartitas (Raspail), Benecke, " Ub. Trias u. Jura i. d. Siid-Alpen " ; 



Geogn. Pal. Beitr., p. 175. 

 1891. Lijtnceras fripartitum (Raspail), Haug, " Les Chaines subalp. entre Gap 



et I)igne " : Bull. Serv. Carte Geol. 



France, vol. iii, p. 79. 

 1897. ,, „ ,, Hoclistetter, " Die Klippe v. St. Veit, 



b. Wien " : Jb. k.k. R.A., vol. xlvii, 



Hft. i, p. 143. 



1905. ,, ,, ., Simionescu, " tjb. Alt, Klaus-Schichten 



Slid. Karpathen " : Verb. k.k. R.A., 

 No. 10, p. 212. 



Description. — This fragment, consisting of two camerae only, 

 is about 7 mm. in length. There is very little difference in the 

 dimensions of the two terminal (septal) surfaces, so that the coiling 

 must have been extremely slow. The thickness of the whorl is 

 nearly equal to the height, which latter is 4'5 min. The section, 

 however, is not circular, but compressed, and the dorsal furrow is 

 very shallow, indicating contact with (but not inclusion of) the inner 

 whorls. The fragment, fortunately, shows a constriction, with a 

 forward bend on the side and a backward sinus on the periphery. 



The suture-line consists of very few elements, namely, a very long 

 but narrow external (ventral) lobe, a bifid external saddle, about 

 the size of the (equally bifid), lateral lobe, and slightly larger than 

 the (also bifid and similar) lateral saddle.^ The second lateral lobe 

 is shorter than the first lateral lobe (which, itself, is shorter than the 

 external lobe), and after the very simple and almost entire second 

 lateral saddle there only is a very small auxiliary lobe, followed by 

 a broad and more or less entire umbilical saddle. In describing the 

 almost identical suture-line of A. tripartitus (Raspail) d'Orbigny ^ 

 apparently had regarded this auxiliary lobe as merely an indentation 

 in the second lateral saddle ("auxiliary saddle " in d'Orbigny), but 

 the continuation of the suture-line on the dorsal side shows it to be 

 a true third lobe. The deep internal lobe is flanked by two long and 

 monophyllic saddles. The " cross " ^ characteristic of the group of 

 Lytoceras fimhriatum (in a wider sense, not only Fimhrilytoceras 

 S. Buckman) is not very pronounced. The septa are rather distant 

 (there are only three in the space of 7 mm.), and they do not inter- 

 penetrate. 



Observations. — The fragment differs in section from the type- 

 figure, and especially from the compressed examples, such as that 

 figured by Quenstedt as A.jjolystoma, by having the thickness nearly 

 equal to the height of the whorl. This probably is not due only 

 to the small size of the present specimen, nor to the fact that the 

 typical specimens of P. tripartitus are generally (elliptically) com- 

 pressed. In examples of this species from the Bathonian of the South 



^ In fig. 6c the first lateral saddle is drawn just a shade too slender. On 

 account of the smallness of these specimens collodiotypes could not be taken. 

 2 Loc. cit., Ter. Jurass., 1842, p. 497. 

 ^ See Pompeckj, loc. cit., Revision, 1893, text-fig. 24 on p. 115, 



