MONOGRAPTUS. 



375 



Figs. 245 a — c. — Monograpius vaiiahilis 

 (Pernor). 



Polypaiy some cm. in length, straight ov with slight tendency to curvature, 

 increasing in breadth from an initial width of '4 mm. to a maximum of rather 

 less than 1 mm. Theca3 twelve to eight in 10 mm., simple tubes slightly 

 expanded in the apertural region, Avith slight overlap ; apertural margins 

 even, horizontal, or slightly introverted. 

 Description. — The polypary may attain a length of 5 cm. or more, Ijut never 

 exceeds 1 mm. in Avidtli and is usually rather less. 



The sicula is small, measuring only 1'5 mm. in 

 length, l)ut reaching "well beyond the level of the 

 aperture of th. 1. 



The apertural margins of the earliest two thecES 

 appear to be slightly everted, but thereafter they 

 are horizontal or even slightly introverted ; the 

 overlap may reach one-third of the total thecal 

 length as a maximum. 



Affinities. — The polypary presents some features 

 in common with both M. nndiis and distal frag- 

 ments of M. NiJssoni. From M. nvdus its diminu- 

 tive breadth should be sufficient to separate it ; and 

 from M. NiJssoni it differs in the form of the poly- 

 pary, and also in the shape of the theca which shows 

 a greater tendency to curvature of the thecal walls 

 and introversion of the apertural margin, approach- 

 ing in these respects the form characteristic of the 

 group of M. Sandersoni. 

 Horizon and Localities, — Gala-Tarannon Beds (zone of M. cris2)us). 

 N. Wcdes : Conway. 



Associates, etc.- — Monog. rariahilis occurs in the zone of M. crisjms associated 

 with Monog. Marri and other forms. 

 GoUcction. — Elles. 



* 



I 



a. Proxini.al end, showing siciila. En- 



largement of part of PL XXXVIl, 

 fig. 5 a. 



b. More distal poi-tion of same specimen. 



c. Distal theca3 in low relief. Enlarge- 



ment of part of PL XXXVII, fig. 5 h. 



Monograptus nudus (Lapworth). Plate XXXVII, figs. 6 a — e. 



1876. Monograptus IlixiiKjeri, Lapwortli, Gcol. Mag., dec. ii, vol. iii, p. 350, pi. xii, figs. 1 a — e. 

 1880. Monograptus Hislngeri var. niuh(s, Lapwortli, Ann. Mag. Nat. Hist. [5], vol. v, p. 156, 

 pi. iv, figs. 7 a — c. 



Polypary 3—5 cm. in lengtli, sti-aight or with ver}^ slight curvature, widening 

 fairly rapidly to a maximum breadth of 2 mm. ThGca3 nine to ten in 

 10 mm., simple broad tul)es, somewhat sacculate in the apertural region, 

 overlapping one-half their length, and Avith even, Avidc, apertural mai-gins. 



50 



