478 BRITISH GRAPTOLITES. 



Olimacog. scalaris, etc. ; in the zone of M. Sedgwickii with M. tenuis, Climacog. 

 scalar is, and the zone fossil; in the zone of M. turriculatus with M. turriculatus, 

 M. Halli, Rastrites maximus, M. dextrorsus, and Petalog. altissimus ; and in the zone 

 of M. crispus with M. crispus, M. exiguus, M. Marri, and M. discus. 



Collections. — Geological Survevof Scotland, Sedgwick Museum, Belfast Natural 

 History Museum, Lapworth, and the Authors. 



Monograptus delicatulus, sp. nov. Plate XLVII, figs. 2 a and b. 



Polypary slender, coiled into an irregular spiral, increasing gradually in 

 width until the maximum diameter of about 1 mm. is attained. Thecae ten 

 in 10 mm., of the general type of those of the mature portion of M. convolutus, 

 but altogether smaller. 



Description. — The curvature of the polypary is usually irregular, the whorls 



rarely lying in one plane, and even then being 



Fig. 333. — Monoqraptus delicatulus, sp. l • m t i • ,i 



n o V unsymmetrically disposed; m some specimens the 



curvature recalls that characteristic of M. inuolutus. 

 The thecas, while resembling those of M. 





\ 



ji 





r 



convolutus, are of uniform type throughout, being 

 never completely isolate and linear ; the thecas of 



i 

 ' | ^ the proximal portion, however, are decidedly more 



distant than those of the more distal part of the 



Specimen showing- character of proxi- 1 J " J ' 



mai thee®. Enlargement of part Affinities. — Superficially Moiiog. delicatulus 



resembles M. convolutus, but the absence of 

 Bastrites -like thecae in the proximal portion, and the greater tenuity of the 

 polypary as a whole, make its identification fairly easy. From M. involutus, which 

 it sometimes approaches in general form, it differs in the more spinose character 

 of the thecal terminations. 



Horizon and Localities. — Llandovery Beds (zones of M. gregarius and M. 

 convolutus). 



S. Scotland : The Corrie, Dobb's Linn ; Sundhope-on-Yarrow, etc. 



Associates, etc. — Monog. delicatulus is a comparatively rare fossil in the zones of 

 M. gregarius and M. convolutus. In the latter it occurs associated with M. con- 

 volutus, M. jaculum, and Cephalog. cometa. 



Collections. — Lapworth and the Authors. 



Monograptus involutus (Lapworth). Plate XLIX, figs. 4 a—c. 



1876. Monograptus intermedins var. involutus, Lapworth, Geol. Mag. [2], vol. iii, p. 316, pi. x, 

 fig. 11. 



