34 INFERIOR OOLITE AMMONITES. 



appearance of Hyperlioceras, they may be said to be intermediate in every sense. 

 My own idea is that they really constitute a distinct species, but as I have not been 

 able to obtain the young of Line, decipiens for comparison, I prefer to leave the matter 

 in its present state. From Lioc. decipiens they may be distinguished by a larger 

 and more ribbed umbilicus, a less compressed form, and a broader, more convex 

 ventral area ; but what further makes me incline to the idea that they may be a 

 separate species is the fact that, although they occur at Bradford Abbas not un- 

 frequently, I have not found one larger than is here depicted. On the other hand, 

 Lioc. decipiens occurs at Sherborne, and, as far as I know, has not been found at 

 Bradford Abbas. 



From Ludwigia comu these forms are separated by an entire difference in 

 ribbing, by their extreme smoothness of test, and by greater thickness ; from other 

 species of Lioceras by their smoothness, quadrate appearance, and more distinct 

 carina ; from Hyperlioceras Walkeri by a smaller carina, and a form less com- 

 pressed oq the outer, but more compressed on the inner area, and a generally 

 larger umbilicus. It must be confessed however, that the separation of Lioceras 

 intermedium from the young forms of Hyperlioceras Walkeri is not always easy to 

 make, and is not so definite as could be wished. One reason for this may be 

 pointed out : the strong carina of the latter becomes much less trenchant as it 

 approaches and reaches the body-chamber ; and, if a specimen in this state be 

 compared with a specimen of the former which lacks both the body-chamber and 

 many of the air-chambers, there is but little difference in the amount of carina 

 present ; so that it becomes important to compare specimens which are alike but 

 distinguishable by the absence or presence of the body-chamber. 



Lioc. intermedium and most of the species of Hyperlioceras have been formerly 

 quoted from Bradford Abbas under the name of Am. Iceviusculus, Sowerby ; from 

 this they may be separated by their possessing (among many points of difference) 

 a concave inner margin and a solid carina. 



The Soiverbyi-zone (Concavum-beds,) at Bradford Abbas has yielded all the 

 specimens in my collection that have their localities recorded. It is not an un- 

 common species, and may probably have been met with at the similar quarries at 

 Half- Way House, Louse Hill, &c, but the matrix shows that none have come 

 from Sherborne, nor any other parts of the district, at least within my knowledge. 



Plate XI, figs. 2, 3, may be regarded as illustrating a type-form of Lioceras 

 intermedin. Figs. 4, 5 show us a large-centred, more compressed, and smoother 

 form. This is the scarcest of the series. In Figs. 6, 7 we have a more ribbed 

 form with a larger umbilicus than in Fig. 2. All these figured specimens have 

 come from Bradford Abbas. 



In Plate XII, fig. 10, a specimen is depicted which shows us where the 

 difficulty lies in separating this species from Hyperlioceras Walkeri. This 



