384 BRITISH GRAPTOLITES. 



times a tendency to become nearly horizontal; usnally, however, it is distinctly 

 everted, as is commonly the case with the other members of this group. 



Affinities. — The British specimens here descriljed seem to come closest to those 

 forms which Perner has described as Monoij. iiltinm.'^, though as a whole the curva- 

 ture of the thecal walls is less pronounced in the British than in the Bohemian 

 s})ecimens. M. cf, iiUimiLS may readily be distinguished from all the species 

 hitherto described by its small size. 



Horizon and Localities. — Lower Ludlow Shales (zone of M. leiiUivardincnsis). 



Lonij Moinifdiii : Near Frochas. Lnlce District: Helm Knot. 



Associates, etc. — The form described above as Mouoij. cf. vltiinus is not a 

 common fossil in the British Lower Ludlow Shales and no really well-preserved 

 specimens have as yet been found, so that its reference to the Bohemian species is 

 still open to question. It occurs in the zone of M. teinttvardincnsis associated with 

 M. leintwardinensis var. incipiens. 



Collections. — Watts, British Museum (Natural History). 



I. B. 1 ((().— Mono/jrdjdi in which the tliecte are bi-form and the polypary has 



dorsal curvature. 



Monograptus revolutus, Kurck. Plate XXXVIII, figs. 1 a — e. 



1882. Monograptus revolutus, Kiiix-k, Geol. Fureu. in Stockh. Forliaudl., vol. vi, p. 299, pi. xiv, 



figs. 2, 3, 4. 

 1899. Mo7iograptiis revolutus, Tornqiiist, Muiiograptidaj of the Sciiuiau Hastrites Beds, Lunds Uuiv. 



Arssk., vol. XXXV, pt. 2, no. 1, p. 11, pi. ii, figs. G — 11. 



Polypary several cm. in length with involute or l)roadly recurved proximal 



portion, widening persistently from a thread-like initial })ortion till the 



maxinnim breadth of rather more than 1 mm. is attained. Tlieca3 eight to 



ten in 10 mm., long narrow tubes of two types ; the early tliecse with outer 



extremity of apertui-al margin retroverted so as to appear somewhat 



beak-like or as if furnished with a tag or rostel ; mature thecfB simple 



tul)es Avith even apertural margins, overlapping two-thirds their length. 



Description. — The form of the j^olypar}^ is characteristic, especially the gradual 



increase in breadth from the thread-like initial portion ; and, as in the case of 



J\[. ri/plins, there is a consideraljle amount of variation in curvature in different 



individuals. 



The early portion of the poly})ary is so slender that its characters are hard to 

 make out ; it appears, however, that the delicate sicula alone forms the termination 

 of the polypary, th. 1 arising some distance above its aperture. 



The mature thecffi closely resemble those of M. ei/phns, l)ut the proximal thecee 

 are of a different type, with a distinct tendency to retroversion of the outer 



