158 Mr. C. Lapworth on new British Graptolites. 



title M. Salteri cannot be identical with that for which the 

 name was originally proposed by Prof. Geinitz. The name, 

 however, is a convenient one. I propose, therefore, to retain 

 it for the form to which it was originally applied by myself. 



Horizon and Locality. M. Salteri , Lapw., is a very rare 

 form, occurring in fragments in the Llandovery strata of Gala 

 and Girvan, South Scotland. 



13. Gyrtograptus Ltnnarssoni, sp. nov. 

 (PI. IV. figs. 12 a, 12 b.) 



Polypary unilateral, compound, monoprionidian. Principal 

 branch long, slender, and elegantly recurved, originating 

 similar simple (or compound?) secondary branches at very 

 distant intervals. Hydrothecae twenty to twenty-five to the 

 inch, adnate in contact only, proximally subtriangular, mucro- 

 nate ; distally tubular, with slightly expanded and more or 

 less everted denticulate apertural margin. 



The branches of this species are about one twentieth of an 

 inch in transverse diameter, if we include the projection of the 

 hydrothecfe ; and they all exhibit the elegant convex curvature 

 characteristic of the genus. They remain of the same general 

 diameter of one twentieth of an inch throughout their whole 

 extent, which, in the longest specimens in my collection, is 

 about 3 inches. 



The first branch is given off invariably between the fifth 

 and sixth hydrothecse, counting from the sicula, the second 

 branch about half an inch beyond. Both imitate the main 

 branch in the direction and amount of their curvature. 



The hydrothecse on the proximal portion of the main branch 

 remind one at first glance of those significant of the Mono- 

 graptidte typified by Monograptus Sedgwickii (Portlk.) . In 

 reality, however, they are of the same general type as those 

 in the main body of the fossil ; they are tubular and adnate, 

 but have their expanded distal extremities abnormally everted 

 and produced. 



The hydrothecas on the branches and the distal portion of 

 the main stem are narrow tubes, inclined at a very steep 

 angle to the axis of the polypary, and very slightly, if at all, 

 expanding towards the aperture. Their distal extremity, 

 however, is very suddenly expanded immediately at the aper- 

 ture, which is distinctly everted, so that the apertural margin 

 makes more than a right angle with the axis of the branch. The 

 resultant denticle is very acute, and is occasionally prolonged 

 into a minute spine directed obliquely. The sudden distal ex- 

 pansion of the theca gives an appearance of constriction below 

 the denticle which is very characteristic. 



