54 INFERIOR OOLITE AMMONITES. 



his Harpoceras aalense with a query. Dr. Vacek, page 72, states that he con- 

 siders that a number of specimens of Harp, opalinum from Cap San Vigilio 

 belong to Haug's Harp, opalinum, var. comptum, especially pi. vi, figs 15 and 16. 

 Having some doubt, however, with respect to these figures, I have not included 

 them in my synonymy ; and in fact I am somewhat doubtful if they should be 

 included in Lioceras at all. Vacek's figures 6, 7, and 13 on pi. vi I recognise 

 as the varietal form comptum, and I am inclined to think that fig. 5, pi. vii, is very 

 closely allied. 



From Lioceras opalinum this variety differs chiefly in the form of ribbing. 

 The striae are not actually fascicled, but the inner portion of the sides of the 

 whorl are periodically bulged in the direction of the striae, and these striae pass 

 continuously over these bulgings which have, when the test is absent, all the 

 appearance of regular ribs, and give to the umbilicus the appearance of being 

 ribbed. The umbilicus is also larger than in Lioc. opalinum, and the walls 

 are much straighter. The sides of the whorls are more parallel and not so 

 depressed on the inner area. When the test is absent this variety has a slight 

 resemblance in its ribbing to Ludwigia Murchisona, but the number of fine striae 

 in connection with a rib or bulge on the inner area shows the difference. This 

 form also somewhat resembles Oramm. aalense (Zieten), but the fine striae again 

 distinguish it from the coarse, irregularly -joined ribs of that species ; the possession 

 too of a concave inner margin is a distinction, not to mention the difference of 

 the sutures. 



I have little doubt that this variety was partly concerned with Dr. Lycett's 

 ideas about the various Ammonites opalinus, aalensis, comptus, &c. He found 

 a most complex state of things, namely, Lioc. opalinum with very fine striae, 

 Gramm. Moorei the same, and with traces of coarser ribs in the centre, Lioc. 

 comptum with (when the test is absent) coarse ribs on the inner area and centre, 

 and Gramm. aalense with coarse ribs ; and, perhaps noticing the similarity between 

 Lioc. opalinum and comptum, he united them but could find no strong reason for 

 separating Gramm. Moorei from Gramm. aalense, or from Lioc. opalinum. By 

 pointing out, later on, the descent or evolution of these various Ammonite -forms, I 

 hope to be able to show that, in spite of a rather deceptive outward appearance, 

 these Ammonites are really somewhat widely separated, and that those ideas 

 partly arose because the real importance of certain characteristics was not fully 

 appreciated. 



I have not so much material belonging to this variety as I could wish. A 

 more extended series would show better both the connection and distinction between 

 the forms with these waves or false ribs and the true Lioc. opalinum. We have, how- 

 ever, first what I imagine to be Reinecke's comptus, PI. XIII, fig. 11, somewhat 



