imperfectly-defined Species of Jurassic &c. Nautili. 389 



columns ; the first contains the new species and also those 

 requiring emendation, the second includes only well-recog- 

 nized species ; to each of the latter, however, the reference to 

 the original description is attached. 



It will be observed that some of the species described 

 below are placed in the subgenus Rercoglossa, Conrad *. The 

 following is Meek'sf emended description of this subgenus : — 

 " Shell more or less discoid, with umbilicus closed or small, 

 and periphery usually rather narrowly rounded \ ; volutions 

 deeply embracing, surface nearly smooth, or with lines of 

 growth ; septa deflected backwards in crossing each side, so 

 as to form a deep, usually angular, lateral lobe/' Type 

 Nautilus orbiculatus, Tuomey §. Trias to Eocene. 



Nautilus Parlcinsoni, Edwards ||, is cited by Meek as 

 belonging also to Hercoglossa. Of this species only two 

 examples are known to us, both from the London Clay — the 

 one figured by Parkinson ^ and also by Edwards, now in the 

 " Sowerby Collection," British Museum, the other from Col- 

 chester. Both specimens are remarkably large ; Parkinson's 

 consists merely of the casts of three chambers, to which a 

 portion of the inner whorls, badly preserved, is attached • the 

 largest chamber is 8 inches in height and 6 inches in width. 

 Owing to the form of the sutures some doubt originally 

 existed as to whether this specimen should not be placed in 

 Aturia. Although the siphuncle is cylindrical, as in Nautilus. 

 the sutures suggested its being the adult of Aturia. Unfor- 

 tunately the inner whorls are so much crushed that the form 

 of the siphuncle in the young shell cannot be ascertained. 

 The specimen from Colchester, which measures 11 inches in 

 diameter, shows, however, that the siphuncle is cylindrical not 

 only in the adult, but even where the diameter of the shell 

 does not exceed 2^ inches. We feel justified therefore in 

 concluding with Meek that Nautilus Parkinsoni belongs to the 



* Amer. Journ. of Conchology, 1800, vol. ii. 110. "2, p. 101. 

 t United States Geol. Surv. Terr. 1876, vol. ix. p. 401. 



or 



coglossa see " Die Cephalopoden der Stramberger Schichten,'' in Oppel and 

 Zittel's ' Palseontologische Mittheilungen,' 1808, Band i. Abth. ii. Atlas, 

 pis. ii., iii., iv. On referring to the ' Catalogue of Scientific Works ' pub- 

 lished by E. Koch, Stuttgart (1880-188(5), we find that this part of the 

 Palaeont. Mitth. is erroneously marked both on the cover and titlepage 

 " Zweiter Band, Erste Abtheilung," whereas it should be " Erster Band, 

 Zweite Abtheilung." 



§ Proceed Acad. Nat. Sci. Philadelphia, 1854, p. 167. 



|| Mon. Eocene Mollusca (Pal. Soc), 1849, pt. i. p. 49, pi. vii. 



^1 ' Organic Remains,' 1811, vol. iii. pi. vii. tig. 15. 



