

DIPLOGRAPTUS. 253 



Var. siccatus, var. nov. Plate XXXI, figs. 3 a— d. 



Another variety of Glyptoq. teretiusculus is dis- 



Pifls. 173 a and b. — Glyptograptus tere- >> •"- _ *' 



tiuscuius, var. siccatus, nov. tinguished by its very small size. It appears never 



to exceed 2 cm. in length and 1 mm. in breadth, 

 and seems to have had a remarkably attenuate 

 test, which is often, indeed, reduced to a mere film, 

 while the virgula is always thread-like and wiry. 

 Horizon and Localities. — Llandeilo, Glenkiln 

 a u Shales. 



, , . . . , , 8. Scotland: Glenkiln Burn; Dol)b's Linn: 



a. Fragment showing proximal end and 



sicuia. Enlargement of specimen Belcraig Burn ; Rein Gill, etc. N. Wales : Tid- 



on same slab as PI. XXXI, figs. 3 a, b. & 



b. Distal thecse. Gwern-y-fed-fach, Lian- dyndicwin. Central Wales .' Pencerriof, near Bnilth ; 



deilo Beds. CoU. Elles. f 



Gwern-y-fed-fach, near Bmlth. 



Associates, etc. — Var. siccatus is fairly common in the Glenkiln Shales and 

 their equivalents ; it occurs associated with Nemag. gracilis, Glimacog. Scharenbergi, 

 Dlcellog. sextans, etc. 



Collections. — Sedgwick Museum, and the Authors. 



Diplograptus (Glyptograptus) dentatus (Brongniart.) Plate XXXI, figs. 4 a — d. 



1828. Fucoides dentatus, Brongniart, Hist, Veget. Foss., vol. i, p. 70, pi. vi, figs. 9 — 12. 



1865. Diplograptus pristiniformis, Hall, Grapt, of Quebec Group, G-eol. Surv. Canada, dec. 2, p. 110, 



pi. xiii, figs. 15 — 17. 

 1868. Diplograpsus pristiniformis, Nicholson, Quart. Journ. Geol. Soc, vol. xxiv, p. 140, pi. v, 



figs. 14, 15. 

 1875. Diplograptus dentatus, Lapworth, Quart. Journ. Geo!. Soc, vol. xxxi, p. 656, pi. xxxiv, 



figs. 5 a, b,d - h. 

 1898. Diplograptus dentatus, Elles, Quart. Journ. Geol. Soc, vol. liv, p. 517. 



Polypary somewhat concavo-convex, short, not exceeding 3 cm. in length, or 

 2 mm. in breadth. Sicnla small, virgella conspicuous ; lateral spines on 

 proximal thecae nnsymmetrically disposed, rarely preserved. Thecre 

 eighteen to twelve in 10 mm., short, having an average length of 1*5 mm., 

 overlap slight, whole of free part of theca introtorted so that the sub-lobate 

 apertnral margin appears oblique in most views ; excavations oblique, ponch- 

 shaped, occupying one quarter of the width of the polypary and one third 

 of its ventral margin. 

 Description. — Glyptog. dentatus presents very varied appearances after com- 

 pression. In the obverse bi-profile view the sicnla has a length of 1 mm., 

 and th. I 1 originates from near its aperture, growing at once outward and 



