ORTHOCERAS CYLINDRACEUM. 7 



Description. — Shell long, very slender, tapering at the rate of 1 : 10. Sec- 

 tion nearly circular. Body-chamber too imperfect for description. Septa very 

 oblique, approximate, from 4 to 5 mm. apart, where the diameter of the shell is 

 about 20 mm. Siphuncle excentric, seen only at the apical extremity. The test 

 is quite smooth. 



Size. — The most complete specimen measures 280 mm. in length, the greatest 

 diameter being 33 mm., the least 5 mm. 



Affinities. — This species bears some resemblance to Orthoceras Nerviense, 

 de Kon., especially in the slenderneas of its form, but the differences separating it 

 from that species are constant and well defined. These consist in the obliquity of 

 its septa and the excentric position of its siphuncle. 



Bemarlcs. — The septal chambers, as is usually the case with the Cork 

 specimens, are filled with crystalline calcite, which has destroyed or distorted 

 the septa and siphuncle. The apical extremity of one of the specimens (PL II, 

 fig. 2 h) is obliquely truncated, and shows the position of the siphuncle in the 

 shape of a small depression or cicatrix, which was originally covered by the shell, 

 the latter having been here broken off in removing the specimen from the rock 

 (PI. II, fig. 2 c). The initial point of these shells is so rarely preserved that I 

 have given a figure of it from a drawing I made under a camera lucida. The 

 extremely slender habit and other characteristic features have led to the ready 

 identification of several examples of this graceful species among the specimens of 

 Orthoceras obtained from the great quarries of Little Island, near Cork. 



Locality. — Little Island,' near Cork. 



Orthoceras cylindraceum, ./. Flcinimj. 



1815. Oethoceea ctli>dracea, J. Fleming. Annals of Philosophy, vol. v, 



p. 202, pi. xxxi, fig. 3. (Not of Sowerby.) 

 ? lSi4. Orthoceeas cylindhaceum, F. M'Coy. Synopsis Carb. Foss. Ireland, 



p. 7. 

 1855. — — — British Pal. Foss., fase. 3, 



p. 569. 

 1888. — — A. H. Foord. Cat. Foss. Cephal., British 



Museum (Natural His- 

 tory), pt. 1, ... p. 102. 



' This is no longer an island, the stream to the north that made it one having been filled up ; it 

 is therefore a peninsula, and is situated in the fine waterway leading from the city of Cork to Cork 

 harbour. 



