432 



BRITISH GRAPTOLITES. 



Monograptus undulatus, sp. nov. Plate XLV, fig. -5. 



Flu. 295. — Monograptus undulatus, 

 sp. nov. 



(?) 1850. Graptolithus Becki, Barraude, Grapt. <le Boheme, p. 50, pi. iii, fig. 15. 



Polypary several cm. in length, slender, flexed, generally with conspicuously 

 recurved proximal end, increasing very gradually in width in the initial 

 portion till the maximum breadth of 1 mm. is attained. Thecse ten to eight 

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

 Sedgioickii, but with a broader retroverted ap'ertural region, involving fully 

 one-half of the thecal length, and occupying fully three-quarters of the 

 total breadth of the polypary. 

 Description. — Throughout its length the polypary has usually both a limp and 



flexed appearance, though occasionally distal frag- 

 ments may appear more rigid : it is uniform in 

 breadth for the greater part of its extent, the 

 Avidening taking place entirely in the proximal 

 portion of the polypary. 



The sicula measures I'l mm. in leno-th, and th. 

 J, which arises near its base, has its highest region 

 on a level Avith the apex of the sicula. 



The isolated, broad, retroverted apertural region 

 of the distal thecse constitutes by far the most con- 

 spicuous feature of the polypary, the adnate portion 

 being relatively insignificant. All the theeae of the 

 proximal portion are small, but they increase steadily 

 in size till the maximum breadth of the polypary is 

 attained. 



Affinities. — Mount/, undulatus presents some 



resemblance to the proximal end of M. Sedgwiclcii&s 



regards the form of the polypary, but the theca? are of a uniform type and remain 



small throughout the extent of the polypary, which is not the case in M. SedgiuicMi. 



Horizon, and Localities. — Llandovery and Tarannon (?), zones of j\I. convolutus 



to M. crispus (?). 



Wales: E. side of old Quarry, 800 yds. N.E. Fagrw Fawr, near Pont Erwyd. 

 Associates, etc. — Monog. undulatus occurs in Wales in the Pont Erwyd district 

 in the zone of M. convolutus, associated with M. Glingani, M. involutus, M. lohifcrus, 

 M. regularis, etc. 



Fragments recalling this species have been detected at higher horizons both 

 in Scotland and elsewhere, but being merely fragments their specific determination 

 is uncertain. 



Collections. — Geological Survey of England and Wales. 



\ 



Proximal end, preserved as a cast, 

 showing sicula. Enlargement of 

 PI. XLV, fig. 5. 



