128 G. C. Crick — On Tmaegoceras. 



3. Tmaegoceras crassiceps, ii.sp. Zone of Arietites Bucklandi : 



neighbourhood of Tubingen (Wiirttemberg). 



4. Tmaegoceras Faronai, G. Bonarelli. Zone of Arietites ohtusus (^) : 



Ponte Grosso, near Ponte Alto (Central Apennines). 



We note that in his paper Dr. Pompeckj makes no reference to 

 Michelin's Ammonites Lacordarii [«ire«3 ^ from the Lower Lias of 

 France, and the object of the present note is to call attention to 

 that species, because it seems to be related to Hyatt's genus. 



Michelin's description of the species is as follows : — 



" A. tests, discoidea ; infractibus 4-5, subinvolutis Isevibus ; lateribus 

 convexis ; canaliculatis propfe penultimum anfractum ; dorso carinato ; 

 carinS, parvS, ad utramque partem slth canaliculata ; ajDertura oblongft, 

 in medio depress^.. 



" Latit. testae [ = diameter] 90 millim. ; latit. inf. ult. [ = height of 

 outer whorl] 30 millim. ; latit. anf. penult. [ = height of penultimate 

 whorl] 20 millim. ; latit. apert. [ = width of aperture] 42 millim. ; long, 

 apertur. [ = height of aperture] 30 millim. 



" Cette espece d'Ammonite, qui est fort rare, et dont je dois la 

 connaissance h men ami M. Lacordaire, ingenieur en chef du canal de 

 Bourgogne, a ete trouvee par lui dans des couches subordonnes du Lias, 

 aux environs de Pouilly en Auxois, departement de la C6te-d'0r. EUe 

 est a r6tat de moule interieur, et ne paralt pas avoir eu une plus grande 

 dimension, attendu qu'on ne voit la trace d'aucune cloison sur les trois 

 quarts du dernier tour. 



" La car5ne, se trouvant plus basse que les deux c6tes exterieurs des 

 canaux qui I'accompagnent, donne au dos de cette coquille 1' aspect d'une 

 corniche. 



" Ma collection et celle de M. de Roissy." 



The desci'iption is accompanied by three figures representing the 

 lateral, apertural, and peripheral aspects of the type-specimen. The 

 suture-line is not figured separately, but it is depicted in the lateral 

 and apertural views of the fossil. 



We have not seen an example of this rare species, nor do we 

 know where Michelin's type is, but there is in the British Museum 

 Collection [register number 37,150] a plaster cast of the type- 

 specimen, and it seems to us most probable that the species belongs 

 to Hyatt's genus Tmaegoceras. To the dimensions given above it 

 may be added that the width of the umbilicus is 40 mm. Michelin's 

 figures give a very good idea of the general form of the specimen, 

 but the suture-line, though probably well shown on the fossil, does not 

 appear to be at all accurately drawn. The suture-line has not been 

 reproduced on the cast. The general form of the species appears to 

 come very near Poinpeckj's new species T. crassiceps and Bonarelli's 

 T. Paronai, and the suture-line, according to Michelin's figure, 

 certainly suggests the characters of that of Von Hauer's Ammonites 

 latesulcatus, the type of Tmaegoceras, rather than that of an Arietites. 



1 H. Michelin: Ma,^. de ZooL, v (1835), Classe 5, pi. 67. 



