352 C. Lapworth — On Scottish MonograptldcB. 



15. MoNOGRAPTUS CYPHUS, sp. nov. Plate XII. Figs. 3 a — d. 

 Monograpsus nuntius, Geinitz; Die Graptolithen, Taf. ii. figs. 



26, 27. 

 GrajHolites Sagittarius, Nicholson ; Quart. Joum. Geol. Soc. vol. 

 xxiv. plate xx. figs. 25, 26. 



Polypary four to six inches in length ; distal portion arcuate, and 

 with an average diameter of one-tenth of an inch; rapidly narrow- 

 ing in the proximal portion, which is either circinate or broadly 

 recurved. HydrothecEe 26 to 28 to the inch, arranged on the convex 

 margin of the periderm at an angle of about 30°, long narrow tubes 

 wdth direct margins, overlapping each other for about half their 

 length ; margin of aperture at right angles with the general 

 direction of the polj^pary ; distal thecee inornate, proximal thecas 

 having their denticles prolonged into distinct spines. 



This is the only fully known species in the present group in which 

 the proximal extremity of the polypary is sharply recurved. In 

 most specimens the broad curvature of the adult portion is con- 

 tinued to the sicula, but not nnfrequently the proximal extremity is 

 decidedly circinate. This peculiar curvature is one of the chief 

 characteristics of the species. 



In the distal portion of the polypary the hydro thecee greatly 

 resemble those in Monogr. jaculum, with which they further agree in 

 the amount of overlap, and in their angle of inclination. They are, 

 however, slightly more numerous propoilionally. In the proximal 

 division, on the other hand, there is a decided expansion immediately 

 below the aperture, and the denticle is prolonged into a well-marked 

 spine, which lies in the same plane with the broad apertural margin. 

 Proximal fragments thus approximate in general appearance to some 

 young examples of forms of the Sedgiviclzii type. These early spines 

 are only seen on well-preserved examples ; nor do they seem to have 

 been invariably present, for comjjressed specimens are often met with 

 in which the proximal portion was almost filiform, and the early 

 hydrothec^ of the type of those of M. intermedins, Carr. 



Uonograptiis nuntius, Barr., shows the dorsal curvature of this 

 species, but judging from Barrande's figure and diagnosis, it appears 

 to be quite distinct. 



Locality. — Birkhill Shales, at Dobbs Linn, Frenchland, Garple, 

 Belcraig. 



16. MoNOGRAPTUS LEPTOTHECA, sp. nov. Plate XII. Figs. 4: a — e. 

 Polypary several inches long, straight distally, and with an average 



diameter of one-tenth of an inch ; gradually narrowing in its proxi- 

 mal portion, which is of remarkable extent, and has a slight dorsal 

 curvature. Hydrothecse exceedingly slender, 18 to 20 to the inch, 

 one-fifth of an inch in length, inclined at an angle of about 10°, and 

 overlapping each other for three-fourths of their length ; free por- 

 tion of each slightly convex; apertural margin short, inclined, 

 concave. 



For the first few inches of length the polypary is as slender as 

 those of the Nilssoni group, and there is an almost imperceptible 



