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Notling* shows conclusively that there are two groups usually 

 included in Lituites that differ in their lines of growth and aper- 

 tures, etc. The" true Lituites have, according to Notling, four 

 principal sinuses, deep ventral and dorsal and shallow lateral 

 sinuses. Schroder has criticised this statement, making out five 

 sinuses and five crests in the apertures and lines of growth. Not- 

 ling'sf statement is substantially the same so far as the larger sinuses 

 and crests are concerned, but Schroder pointed out that the dorsal 

 sinus was subdivided by a central crest into two smaller sinuses. 

 The correct way of describing the sinus of the inner side, judging 

 by the growth and development, is to regard it as the dorsal sinus, 

 and the dividing crest and minor sinuses being developed later as 

 minor or subsidiary dorsal crest and sinuses. 



Holm| has confirmed this view and, with the fine materials at his 

 command, has figured the dorsal sinus spreading at the base and 

 divided by a slight reentrant crest, which is also reflected in the 

 lines of growth on that side of the living chamber, while the ven- 

 tral sinus is deeper and narrower and undivided. These facts 

 increase the differences of the aperture between Lituites and Ancis- 

 troceras, and at the same time the slight median crest in the aper- 

 ture and lines of growth on the dorsum of Lituites makes the 

 affinity with Cycloceras and Ancistroceras clearer than it would 

 otherwise be. The crest and sinuses are also very much more pro- 

 nounced in Lituites, and the enrolled portion of the whorl is con- 

 tinued longer and is more closely coiled, the whorls being in con- 

 tact for between three and four volutions. Holm's figures of Lit. 

 lituus show that on the early part of the straight whorl the lines of 

 growth are entirely different from the later parts of the same whorl. 

 The outlines have a slight, shallow dorsal sinus, the median dorsal 

 crest not having yet been developed. The same peculiarity is 

 observable in Notling' s figure on a part of the shell preserved and 

 show the lines of growth at about the same stage of growth, and 

 also upon Lossen's figure of the same species. There are also 

 decisive costations on the coiled whorls, which are similar in both 

 of these figures. These in the younger substages are bent apically 

 towards the venter and forwards towards the dorsum, and have not 

 the more complex curves of the older stage. 



*"Beitr. z. Kennt. d. Ceph. a. Silurg. d. Prov. Ost-Preussen," Jahrb. d. k. Prcuss. Geo!. 

 Landesanst. u. Bcrgak., 1883, p. 126 et seq., and Zcitsch. Deutsch. Oeol. Qesett., 1882. 

 f " Untersuch. u. Sil. Ceph.," Pal. AM., Dames et Keyser, v, heft iv. p. 44. 

 tAftryck. Geol. Form. Stockholm Forhandl., xiii, 1891. 



