72 INFERIOR OOLITE AMMONITES. 



is probable that the change from a pointed to a rounded process accompanies 

 the change in the ribs.) The open umbilicus of this specimen is quite in 

 accordance with what may be observed in the inner whorls of the larger 

 specimen on the same plate (fig. 1). I collected this fossil at Bradford Abbas. 

 In PL VI under the name " var. A," which, however, may now be erased, 

 is depicted the slightly thinner form of Lioc. v-scriptum with smaller umbilicus. 

 This and another specimen of Lioc. concavum, which has about one inch more 

 in the length of whorl, are by far the largest specimens of any form of the species 

 or its varieties with which I am acquainted ; about half a whorl less when the 

 specimen is perfect, or even smaller, are the sizes more usually found. These 

 two specimens I obtained at the same place, namely, the railway-cutting at Bradford 

 Abbas, and to the best of my recollection on the same day ; but specimens of this 

 size must be scarce because I do not remember to have obtained another, nor 

 does my father's collection exhibit anything so large. PL IX, figs. 5, 6, show 

 a small specimen of this form with the narrow umbilicus from Bradford Abbas. 

 The carina in this figure is rather too prominent. On PL X, figs. 5, 6, we have 

 the largest specimen which I possess of the thicker form with broader umbilicus. 

 The carina, where the whorl enters the aperture, seems, on account of a blot, too 

 acute, but is correct at the top and bottom of the figure. The specimen was 

 obtained by my father, and, judging from the matrix, came from Bradford Abbas. 



The suture-lines of Lioc. v-scriptum are shown in PL A, fig. 16, and a portion 

 in situ, PL IX, fig. 4. The former, which was taken from the specimen figured 

 on PL X, figs. 5, 6, shows all the characters of the suture-line of Lioceras, with 

 a well- developed accessory lobe in the siphonal saddle, and a gradually decreasing 

 array of lateral and auxiliary lobes (of the latter there are four fairly well 

 pronounced). The latter figure shows the way in which the preceding lobes are 

 penetrated by later lobes, a character which, besides perhaps indicating slower 

 growth, gave greater support to the side, and was certainly a most persistent 

 feature in the genus Lioceras. 



The other varieties op Lioceras concavum (Sow.). Plate VIII, figs. 3 — 8; Plate 

 IX, figs. 8—10 ; Plate X, figs. 3, 4, and 9 ; Plate XV, figs. 5, 6. 



If we examine all the varied forms which seem to arrange themselves under 

 the general title Lioc. concavum and varieties, we shall observe, as I pointed out in 

 treating of the type (p. 57), a very general resemblance in certain important features, 

 and that they may be divided roughly into two classes, the one possessing sig- 



