MONOGRAPTUS. 



455 



Figs. 313 a— d. — Nonograptus nodifer, 

 Tornquist. 



Polypary small, slender, arcuate, with double curvature at the proximal end, 

 increasing gradually in breadth till a maximum of '9 mm. is attained. 

 Thecae on the concave margin, twelve to ten in 10 mm., of the general type 

 of M. lobiferus, but with greater retroversion and torsion of the whole 

 apertural region, the resulting lobe occupying proximally fully one-half of 

 the breadth of the polypary, but distally rather less. 

 Description. — The polypary is curved in a manner which strongly resembles 

 that of M. exiguus, though as a rule the flexure is somewhat stiffer and the 



polypary somewhat larger, specimens of 4 — 5 cm. in 

 length being of fairly common occurrence. The 

 polypary widens more gradually than M. exiguus, 

 and attains a greater breadth, so that fragments 

 from the proximal portion may actually be narrower 

 than corresponding portions of that species. 



The sicula is small, measuring -9 mm. in length, 

 th. 1 arising; from near its base. 



The thecae when compressed usually recall those 

 of M. runcinatus as respects their adnate region, the 

 ventral wall not infrequently presenting the appear- 

 ance of expanding in the direction of the apertural 

 lobe of the thecae next below; in specimens preserved 

 in relief, however, this is not such a conspicuous 

 feature. 



The appearance described by Tornquist as a 

 "double fold" is visible in many of our specimens 

 preserved in relief, but appears to us to be a conse- 

 quence of the extreme torsion of the apertural region, 

 to such an extent indeed, that the appearance pre- 

 sented almost suggests an excavation of the upper 

 part of the ventral wall for its reception. 



Affinities. — As will be gathered from the above description, Monog. nodifer 

 presents many points of resemblance to M. exiguus, and, in fact, in poorly preserved 

 specimens is almost indistinguishable unless the more gradual and persistent 

 widening of the polypary can be made out, In well-preserved specimens there is a 

 greater amount of retroversion and torsion of all the thecae of M. nodifer, only a 

 few of the most distal thecae of M. exiguus showing anything of the kind, and then 

 in a less degree, so that in such specimens the distinction is comparatively easy. 



Horizon and Localities.— Gala-Tarannon Beds (zones of M. crisjpus and M. 

 turriculatus). 



8. Scotland : Grennan Quarry, Drummore, Mull of Galloway ; Hill End, N. of 

 Clovenfords, Melrose, etc. Wales : River Twymyn, Llanbrynmair ; Forge Corner, 



60 



a d 



a. Complete specimen, in partial relief, 



showing sicula. River Twymyn, 

 near Llanbrynmair; Brynmair Beds. 

 Coll. Wood. 



b. Distal thecas, in partial relief, showing 



well-marked lobe. Enlargement of 

 part of PI. XL VI, fig. 2 c. 



c. Small fragment, in full relief. Llany- 



stwmdwy, near Criccieth. Coll. 

 Fearnsides. 



d. Fragment in full relief, showing the 



" double fold " appearance and " ex- 

 cavation" characteristic of this 

 form. Llanystwmdwy. Coll. Fearn- 

 sides. 



