150 Mr. C. Lap worth on new British Graptolites. 



distinct and more or less flexuous horizontal spine ; apertural 

 margin short, concave, oblique, and destitute of ornamen- 

 tation. 



This peculiar little species is recognizable at a glance by 

 its form and diminutive size, and more especially by the 

 remarkable ventral spine, which does not originate from the 

 denticle of the apertural margin (as is generally the case with 

 this ornament), but proceeds from the upper angle of a deep 

 excavation in the ventral margin of the theca, as in Mono- 

 graptus vomerinus, Nich. This spine, although very slender, 

 is always conspicuous, proceeding outwards to a distance 

 occasionally equal to that of the entire width of the poly- 

 pary itself. It appears to have been somewhat flexible ; for 

 no two consecutive spines lie precisely at the same angle 

 of inclination. The distal prolongation of the virgula is 

 general in this species ; it rarely exceeds in length the poly- 

 pary itself. 



Horizon and Locality. Monograptus leintwardinensis oc- 

 curs in great abundance in the Lower Ludlow rocks of Leint- 

 wardine (Hopk.), and in the same general horizon near 

 Presteign, New Radnor, Ludlow, Buttington, &c. 



2. Monograptus Salweyi, Hopk. MS. 

 (PL IV. figs. 2 a, 2 b.) 

 Monograptus Salweyi, Hopkinson, Geol. Magazine, 1873, p. 520. 



Polypary straight, rigid, of unknown length, having a 

 general diameter of one twelfth of an inch, exclusive of the 

 extension of the apertural spines. Virgula stout, distally 

 prolonged. Hydrothecse twenty-five to the inch, inclined at 

 an angle of about 45°, straight, narrow, tubular, overlapping 

 each other for four fifths of their length ; free portion slightly 

 expanded, with subvertical apertural margin furnished dis- 

 tally with a stout and rigid horizontal spine. 



Only a single and fragmentary example of this form has 

 been detected ; but its characters are so unique that there can 

 be no hesitation in assigning it a distinct specific title. The 

 distal portion of the polypary only is preserved to us ; and as 

 there is no appearance of proximal contraction, it is impossible 

 to speculate upon the total length. The most remarkable 

 peculiarity of this species is afforded by the anomalous features 

 of the apertural margin of the theca. The plane of the aper- 

 ture appears to lie almost parallel with the ventral edge of 

 the polypary, or but very slightly oblique ; its inferior or 

 proximal sinus is marked by a minute denticle, never very 

 conspicuous. The edge of the aperture itself is concave and 



