20 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Description. — Shell probably elongated, tapering at the rate of about 1:9. 

 Section elliptic in the ratio of 6:5. Body-chamber incomplete; it shows a well- 

 marked constriction towards the anterior extremity, indicating the proximity of the 

 aperture. The septa are slightly oblique, approximate, and arranged with great 

 regularity. They are 6 mm. distant where the diameter of the shell is 43 mm. ; 

 they are therefore about one-seventh of this diameter apart. Only four or five of 

 the septa are seen, as the test covers the rest of the shell. The siphuncle has been 

 destroyed by the deposit of crystalline calcite filling the chambers. It was 

 doubtless cylindrical. The ornaments of the test consist of a multitude of fine 

 longitudinal, parallel, nearly equal, straight striae, two or two and a half of which 

 occupy the space of 1 mm. When looked at through a pocket-lens of low power, 

 they are seen to be not perfectly straight, but slightly wavy, though they preserve 

 on the whole a very even course, parallel to each other and to the longitudinal 

 axis of the shell. A broad and shallow groove runs the whole length of the 

 specimen ; on each side of this groove there is a slight swelling, upon which the 

 transverse lines of growth stand out prominently, the longitudinal ornaments 

 being here scarcely perceptible. 



Affinities. — In its ornamentation this species may very well be compared with 

 Orthoceras (Actinoceras) striatum of J. Sowerby, 1 but here the comparison ceases ; 

 the septa in the former are twice as numerous as they are in Sowerby's species, 

 the shell is of a more slender habit, and the siphuncle is cylindrical. From 

 0. lineale, de Koninck ~ (probably identical with 0. striatum, J. Sowerby), it is 

 distinguished by the same characters. 



Remarks. — The present species is represented only by a fragment (PI. VI, 

 fig. 2 a). Longitudinally striated species are apparently of rare occurrence ; 

 only two have come into my hands during five years of collecting in Ireland, 

 and Sowerby's species (from Black Rock, near Cork) makes the third Irish one. 

 The species described by de Koninck under the name of Orthoceras lineale, if 

 valid, makes a fourth species. I am not acquainted with any species from the 

 English or Scotch Carboniferous rocks having this kind of ornament. 



Locality. — Clane, county of Kildare. 



1 'Min. Conch.,' vol. i, p. 129, pi. lviii. 



2 ' Calc. Carb. Belg.,' 1880, pt. 2, p. 79, pi. xli ; pi. xliii, fig. 8. 



