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asserts that lines of growth in Lituites and Ancistroceras are similar 

 and certainly this appears to be in part true. There are distinct 

 inflections indicating the probable presence of five crests and five 

 sinuses as this author states. These are perfectly well shown in Anc. 

 Torelli, as figured by Remele, and in his Anc. (Stromb.) Bolli. 

 But in all of these there are other characters not found in Lituites 

 or in other genera of this family which separate these fossils as a 

 distinct group in my opinion of generic value. 



While the lines of growth are similar, they show that differences 

 must have existed in the form of the crests and sinuses on the dorsal 

 side of the aperture corresponding to the slight development of the 

 median minor crest and paired minor sinuses on the dorsal side. 

 In fact when one describes the curves of the dorsal lines of growth 

 as indicating a dorsal crest in place of a lobe, he is coming nearer 

 to the actual aspect than when he correctly classifies the outlines as 

 a broad sinus subdivided by a minor crest and secondary sinuses. 

 In other words, the great dorsal sinus of Lituites has reached the 

 disappearance point in this genus during the ephebic stage but has 

 not entirely vanished except perhaps in some species. It, also, as 

 is well known, is a much larger, broader form, spreading out rapidly 

 in the outstretched or free part of the whorl. It is also plain that 

 the enrolled part or young shell of Ancistroceras has fewer and less 

 closely coiled whorls than in Lituites. Thus A. Torelli, as figured 

 by Remele, has only one to one-half volutions enrolled and these 

 do not touch although closely approximate. In fact the young of 

 Ancistroceras are only coiled during the nepionic stage, and perhaps 

 ananeanic substage, and the figures show much larger, stouter whorls 

 even at the apex than in Lituites. The figures of Remele of 

 A. Torelli and of Notling of A. undulatum are very careful studies, 

 and exhibit the changes in development of the lines and annuli. 

 These have in the neanic stage subacute, narrow crests, lateral 

 sinuses rising to prominent ventrolateral crests and between these 

 on the venter is a deep, broad median sinus, thus resembling those 

 of Cyclolituites. The paraneanic substage is present on the early 

 part of the outstretched whorl in Torelli and undulatum. 



The siphuncle is also much larger in this genus than in Lituites. 

 The study of the pseudo-septa by Holm led him to observe the 

 siphuncle in A. undulatum and Torelli and his description is as 

 follows :* " Der siphonen scheint mir wenigstens auf der einen oder 



* PaZeontol. Abh., Dames u. Kayser, iii, hft. i, "Organiz. Silur. Ceph.," 1885, PI. xxi. 



