338 R. Etheridge,jun. — On Turrilepas and Annelid Jaws — 



one inch and an eighth in length, hy an eighth in width. Only 

 the impressions of two plates are present. If this represents any- 

 thing approaching the form of the original organism, it certainly 

 differs from any with which the writer is acquainted. There are 

 traces of four rows transversely, and from twelve to fifteen in a row 

 longitudinally, but the entire Turrilepas is not preserved. 



The proportions of the individual plates are different to those of 

 the English Wenlock species, T. Wrightii, de Kon., sp., 1 being much 

 more elongated and very slender, and the growth imbrications finer 

 and closer. Some of the plates, as in Fig. 1, are not unlike T. Scotica, 

 mihi, 2 only wanting the extreme kite-like outline of the latter, and 

 fine drawn-out superior end. 



The plates contained in this slender body, Fig. 1, I believe to 

 represent a different species to that represented by Fig. 3. The 

 latter agrees better with T. WriylitH, 3 or an undescribed species which 

 occurs in the Wenlock rocks of the Pentland Hills, N.B., than it 

 does with either of the Bohemian species. The subject of Fig. 3 is 

 a short, obliquely deltoid, or triangular, very inequilateral plate, 

 strongly carinate excentrically, and with a short pointed apex, the 

 lower margin being doubly sigmoidal, like the successive surface 

 imbrications, which are much coarser in this form of plate. These 

 transverse lines describe two unequal sigmoidal curves in their course 

 across each plate. 



In a third form of plate, not figured here, the carina is central 

 and narrow, the surface on one side plain, the other with very 

 marked imbricating laminar striae deflected downwards almost at 

 a right angle to the carina, and strongly denticulating the margin 

 of the plate. 



Several cancellated plates occur, but there is no resemblance 

 between them and those figured by Barrande from Bohemia, 4 or 

 T. Scotica, mihi. The cancellated plates are elongately triangular- 

 oval, the carina simple, and slightly excentric. The imbricating 

 lamina? are distant, except along one margin, where they suddenly 

 become parallel to the latter, and are quite contiguous to one 

 another. Towards the narrower end of these particular plates the 

 laminae become concentric, thus cutting off the apical portion, which 

 is depressed and round, although not perfectly central, nor truly 

 apical as regards the margin of the plate. 



To sum up, there seems to be little doubt that at least two species 

 exist in the Wenlock rocks of N. S. Wales — one represented by 

 Figs. 1, 2, 4, and 5, and a second by Fig. 3. To the former I con- 

 ceive belong the cancellated plates Figs. 4 and 5, and for these, 

 including the series of plates composing the somewhat disunited 

 sac-like body, is suggested the name of Turrilepas Mitchelli, mihi. 



The remaining plate, Fig. 3, will for the present remain as 

 Turrilepas, sp. 



1 Geol. Mag. 1865. 



2 Mon. Sil. Foss. Girvan, 1880, fasc. 2, p. 214, t. 14. f. 22-24. 



3 Woodward, Q..J.G.S. 1865, vol. xxi. t. 14; Geol. Mag. 1865, p. 470. 

 * Syst. Sil. Boheme, 1872, i. Suppl. 



