Revieics — J. M. Clarhe — On the Genus Nnnno. 561 



true base nor their upper boundary is visible. The pebbles of 

 Carboniferous Limestone in the conglomerates point to a post- 

 Carboniferous age, and the physical characters of both divisions 

 are identical vpith those of the Permian rocks of the North of 

 England, and more particularly with those of the Lake District, 

 of the Vale of Eden and Barrow Mouth, described by Sedgwick, 

 Harkness, Binney, Eccles, and Nicholson. It is clear that north- 

 eastern Ireland, the northern part of the Isle of Man, and the area 

 of the Lake District, including the Vale of Eden, were parts of 

 the same Permian marine basin, in which, as it approached southern 

 Lancashire, the waters gradually were more highly charged with 

 mud, the calcareous element being conspicuous in the one, and being 

 replaced in the other by thick accumulations of marl. 



I?, S ^7- I E AA7" S. 



I. — Nanno, a new Cephalopodan type. By J. M. Clarke. (The 

 American Geologist, vol. xiv. pp. 205-208, pi. vi. October, 1894.) 



THE author's description of this Cephalopodan type is based upon 

 " seven specimens obtained from the Trenton shales of Min- 

 neapolis and from the Galena shales at Chatfield, Minnesota." All 

 the specimens represent only one species, for which the name 

 Nanno aulema is proposed. The species has the appearance of a 

 short, stout, fusiform Endoceras, tapering rather rapidly to a some- 

 what acute point. The siphuncular tube (sipho) is marginal, and 

 occupies nearly one-half of the diameter of the shell. " The septa 

 are gently and regularly concave over most of their surface, but 

 abruptly deflected immediately above the sipho." The conical 

 posterior portion is aseptate ; it is formed by the inflation of the 

 siphuncular tube, which is covered by a thin layer of the test. As 

 in the genus Endoceras, the siphuncular tubes (siphones) are some- 

 times found detached from the rest of the shell ; they have then the 

 appearance of small Belemnites, whose posterior extremity is some- 

 what inflated ; the cylindrical portion bears oblique impressions as 

 in Endoceras, but these are interrupted on that side of the tube which 

 was in contact with the shell-wall. The siphuncular tubes are 

 " completely solid in the apical portion for usually about one-half 

 the length of the prseseptal cone, but in some examples the solidifi- 

 cation extends for the entire length of the cone and into the 

 cylindrical part of the tube. The cavity of the sipho above this 

 filling is a narrowly conical chamber, whose walls gradually become 

 thinner from the apex upward, their upper edge appearing to be 

 rounded ofi"and finished." 



" The substance of the siphonal cone and walls is invariably very 

 compact, radially crystalline calcite." " Cross-sections of the cone 

 in both directions indicate * * that this is composed of at least 

 two invaginated and consolidated sheaths," similar to those found 

 in Piloceras, Vaginoceras, and Endoceras, but the author did not 

 observe any traces of a tube connecting the apices of these sheaths, 

 such as has been described in Piloceras and Endoceras. 



DECADE IV. VOL. I. — NO. XII. 36 



