98 L. F. Spatli — On Scldotheimia Greenoughi. 



Greenoughi, M.C. T. 132," as well as a very large specimen of 

 a diameter of 520 mm., the history of which is unknown. Although 

 the catalogue handed to the Museum with the collection records, in 

 J. de C. Sowerby's handwriting, only one example of A. Greenoughi, 

 it is probable that the Sowerby Collection originally included three 

 specimens, namely: (A) the figured specimen (holotype) which, 

 according to Wright, 1 is decomposed and cannot now be traced ; 

 (B) the smaller of the specimens afore-mentioned (B.M. Geol. Dept., 

 ISTo. C 17640); (C) a larger specimen of 440 mm. diameter (B.M., 

 TSo. C 17641). 



The smaller of these two paratypes, i.e. specimen B, best 

 illustrates the species, and is, therefore, now taken as the lectotype 

 (see Plate IV). It is suggested that Wright did not know of the 

 existence of this specimen when he described the form. It measures 

 about 230 mm. in diameter, but has two-fifths of the outer whorl 

 missing and also the innermost whorls. The specimen consists of 

 a cast in iron-pyrites filled loosely with calcite crystals in large 

 scalenohedra. Its body-chamber portion, marked "Part of the large 

 specimen which is in fragments", now measures only about one- 

 quarter of a whorl, but, to judge by the umbilical junction preserved 

 on the previous whorl, originally consisted of at least three- quarters 

 of a whorl. On the accompanying Plate IV this body-chamber 

 fragment is omitted, but it would reach from a (the end of the septate 

 stage) to b. The complete Ammonite then measured some 320 mm. 

 in diameter. This body-chamber portion consists of a bluish-grey 

 limestone, weathering to a softer and lighter-coloured stone, typical 

 of Somerset and especially the Bath-Keynsham district. 



The specimen cannot be the entirely septate Ammonite figured by 

 Sowerby, 2 for it is of quite a different appearance. Even if it had 

 been entire and in good condition at the time of preparation of 

 Sowerby's figure, the short distance of its conspicuous last suture 3 

 from the end of the costate stage would almost certainly have been 

 correctly indicated by Sowerby. The dimensions agree, however, as 

 the following figures show, testifying to the probable accuracy of 

 Sowerby's delineation. 



Diameter. Height. Thickness. Umbilicus. 



Sowerby's figure . 113 mm. 47 per cent ? 24 per cent 21 per cent 

 Specimen Bat . 140 „ 48 ,, ?26 ,, 21 ,, 



at . 203 ,, 47 ,, ?23 ,, 21 „ 



Now Wright states that the specimen he studied had a diameter 

 of 440 mm. But this diameter agrees with the second specimen (C) 

 of the Sowerby Collection, whereas the one that Wright 4 figured 



1 T. Wright, Lias Ammonites (Mon. Pal. Soc), 1882, p. 384. 



2 Mineral Conchology, vol. ii, p. 71, pi. 132, 1816. 



3 This distance, in the large, comparable specimens, amounts to about one 

 whole whorl, and it is probable, therefore, that Sowerby's figure is reduced to, 

 perhaps, as much as one-third of the original diameter, especially since he 

 states that specimens vary in size from 12 to 18 inches in diameter. The 

 suture-line itself has the lateral saddle higher and larger than the external 

 saddle, and is apparently of a Schlotheimia pattern. Only the last ones at 

 about 200 mm. diameter are visible (at a in the figure), but they are, 

 unfortunately, not clearly traceable. 



4 T. Wright, op. cit., pi. xliv. 



