444 Q. C. Crick — Cephalopods from the Tyrol. 



form is now elliptical, the longer and transverse diameters being about 

 130 and 82mm. respectively; the ellipse is obliquely truncated at 

 one end by a natural fracture. Portions of only two whorls, the 

 outer and the penultimate, are preserved ; only a little more than 

 one-half of the outer whorl is present, but the greater part of the 

 penultimate whorl is more or less imperfectly preserved ; the innermost 

 whorls are not shown. At the anterior end of the specimen, that is, 

 near one end of the longer diameter, the height of the whorl is about 

 33 mm., and the width of the umbilicus about 100 mm.; whilst at 

 a quarter of a whorl back, that is to say, near the end of the 

 transverse diameter, the height of the whorl is only 23 mm., and the 

 width of the umbilicus 41mm. The whorls were evidently com- 

 paratively narrow, and very evolute, with apparently scarcely any 

 inclusion. The ornaments consist of simple, nearly straight, forwardly- 

 inclined, and not very widely-spaced ribs, but it is difficult to estimate 

 the exact width of the interspaces, or even the exact width (or height) 

 of the whorls, because, owing to the distortion which has taken place 

 during fossilization, the whorls are relatively narrower, and the ribs 

 further apart near the extremities of the transverse diameter than 

 they are near the extremities of the longer diameter. The ribs are 

 nearly straight on the sides of the whorl, but turn somewhat abruptly 

 forward almost close to, though without crossing, what is now the 

 margin of the specimen. Although rather prominent, the bend of the 

 rib does not appear to have been raised into a distinct tubercle. 

 Unfortunately the fossil is so crushed that the form of the periphery 

 cannot be seen. The margin just referred to, however, does not 

 appear to have been at the centime of the peripheral area, but rather to 

 have been the ridge bordering that area on one side, and separated 

 from a median keel by a more or less distinct longitudinal groove. 

 Near the earliest part of the outer whorl that is preserved there 

 appear to be traces of three or four suture-lines, so that it would seem 

 that the greater part of the outer whorl now present formed part of 

 the body-chamber; no suture-lines are visible on the penultimate 

 whorl. Naturally the suture-lines have participated in the general 

 distortion of the specimen, and are now very obscure ; they do not 

 appear, however, to have been ceratitic. 



The condition of the specimen renders any identification extremely 

 difficult. The form of the peripheral margin and the general character 

 of the suture-line, so far as it can be made out, seem to remove it 

 from such genera as Ceratites and its allies, whilst these characters, 

 together with the nature of the ribbing, suggest its reference to the 

 Arietidse. The fossil bears a striking resemblance to a figure given 

 by Parona ^ of a specimen from the Lower Lias ( C. Bucklandi-zone) of 

 Alpe Loggio sopra Ponna (Vail' Intelvi), Lombardy, that he refers 

 with a query to Dumortier's species Arnoiddi,'^ a species included 



1 C. F. Parona, " Contribuzione alia conoscenza delle Ammoniti liasiche di 

 Lombardia," pt. iii, Ammoniti del calcare nero di Moltrasio, Careno, Civate nel 

 Bacino lariano (Mem. See. Pal. Suisse, vol. xxv, 1898), p. 11, pi. xv, fig. 5 

 (Arietites {Arniocerqs) Arnouldi). 



^ E. Dumortier, Etudes paleontologiques sur les depots jurassiques du Bassin du 

 Rhone, pt. ii, 1867, p. 27, pi. v, figs. 1,2; pi. vi, figs. 1-6. 



