Vol. 56.] 



FORMATION AND ITS GRAPTOLITE-FAUNA. 



481 



Fig. 23. — Monograptus 

 crinitus, sp. nov,, from 

 Lower Winnington Lane, 

 Long Mountain (x5). 

 d 



li 



a 



that of M. scanicus, as is also its relation to the first theca. It is 

 about 1*4 mm. (*055 inch) long, and 6 or 6| times as long as wide 



Aperture concave, with spines. The 

 first theca arises at a distance of from 

 a half to a third of the length of the 

 sicula from the aperture of the sicula. 



ThecaB. — Fourteen to eighteen in 

 the inch (five and a half to seven in 

 1 cm.), inclined to the axis at an 

 angle of 5° to 10°. Long narrow 

 tubes, expanding gradually towards the 

 aperture, the upper wall of which bends 

 over like a small hook or claw. In the 

 distal thecaB this claw-like portion is 

 blunter and less hook-like. Length of 

 proximal thecaB=l-9 mm. ('063 inch), 

 whereas that of the more distal is 

 1*6 mm. (-055 inch). ThecaB in contact 

 only. 



Affinities, etc. — This species 

 seems to be quite distinct from any 

 other Lower Ludlow graptolite yet 

 described. It may be readily distin- 

 guished by : — 



(1) Its delicate thread-like form ; 



(2) The hook-like shape of the thecaB ; and 



(3) The distance apart of the thecae. 



1 



w i -I 



a = Enlargement of fig. 

 in PL XXV. 



b == Proximal extremity. 

 c. d=More distal thecas. 



It is a matter of considerable difficulty to distinguish species 

 with such very slender forms one from the other, owing to the 

 impossibility of making out the necessary minute details ; hence 

 the general form of the polypary in these cases must be the main 

 guide. It is mainly on this ground that I consider this species 

 distinct from M. Barrandei (Suess), though it resembles that species 

 in its slender shape and number of thecaB to the inch. M. Barrandei, 

 however, is straight or very slightly curved distally, while M. crinitus 

 is markedly flexuous and curved throughout. The type of theca, too, 

 is rather different in the two forms, so far as one can judge in such 

 minute cells : the apertures in M. Barrandei are (according to Prof. 

 Lapworth) blunt, and the apertures of the proximal thecaB hardly 

 project at all from the ventral margin ; whereas in M. crinitus the 

 apertures are prolonged into a pointed claw or hook, and those of 

 the proximal thecaB project almost as much from the ventral margin 

 as do those of the adult thecaB. It is possible that M. Barrandei 

 of JaBkel may be referable to this species, but the description and 

 figures are too meagre to afford sufficient evidence. 



Locality. — Lower Winnington, on the north side of the Long 

 Mountain. 



Horizon. — Zone of M. Nilssoni. 



Associates. — M, varians, M. Nilssoni, and Retiolites sp. 



