NERIN.5^A. 223 



posterior marginal rim. No signs of spiral ornamentation have as yet been 

 detected, though we should expect fine spiral lines in the apical whorls. 



The body- whorl is short, flat or scarcely hollowed, and angular. The aperture is 

 subrhomboidal, and where the specimens are complete or nearly so (fig. 3 a) there 

 is no trace of the folds which are so conspicuous in the section of the spire.^ Canal 

 short and moderately reflexed. The section exhibits six folds, some of which are 

 very complex. On the outer wall the anterior fold is very wide, and has three or 

 four small angular indentations, whilst the posterior fold is small and deep, but 

 almost simple. Of the three folds on the columella the lower one is the largest 

 and square-headed; the fold on the posterior wall occupies a large space and 

 bifurcates unequally. Altogether the space for the animal in the whorls of the 

 spire must have been excessively small, and specimens, especially from the 

 Lincolnshire Limestone, when cut longitudinally, exhibit very whimsical figures. 

 There are indications, however, that this system underwent modification in the 

 later whorls, and that possibly it was non-existent in the body-whorl. But other 

 interpretations of these appearances have been suggested. 



Var. ooNioA, Witchell. 



1887. Neein^a conica, Witchell. Op. cit., p. 30, pi. i, fig. 2. 



Description : 



Spiral angle . . . .13°. 



Height of whorl to width . . . 1 : 1*85. 



Length . . . . .75 mm. 



In the apical whorls there is a thick sutural prominence, which gradually 

 passes off into a step-like increase of the anterior whorls (well seen in figs. 4 a 

 and 4 5), which are short and flat, and without ornament. The type specimen 

 (fig. 4 a) did not enable Mr. Witchell to ascertain the internal structure of his 

 " Nerinaea conica" but specimens since obtained by myself (fig. 4 I) show that the 

 section is practically identical with that of Ptijfjmatis Cottesiuoldise, from which it 

 is distinguished by its more conical figure and by the strap-like arrangement of the 

 lower whorls. The forms 4 c and 4 d represent short conical specimens of 

 Ptygmatis Cotteswoldise. without the strap-like arrangement of the anterior whorls, 

 characteristic of the var. conica. Such specimens are very abundant in the Oolite- 

 Marl horizon of Longridge, and may possibly be regarded as abraded specimens 

 of the var. conica. At all events, they are short conical varieties of Pty(j. Gottes- 

 woldise with very short whorls. 



Relations and Distribution. — The peculiar internal character serves to dis- 



^ This seems to have beou the case with other species of ]<lerinvea. iSee remarks, p. 195. 



