174 Mr. C. Lapworth on new British Graptolites. 



the Girvan examples the test appears to have been more or 

 less punctate. 



We are now in a position to harmonize the apparently con- 

 flicting appearances presented • by the forms noticed at the 

 commencement of this description, and to show that they 

 may have all been derived from this single species. In 

 PI. V. fig. 27 d we see the rhomboidal theca and zigzag 

 ventral margin presented in Carruthers's original figure of his 

 D. tricornis. In the same figure the general aspect of the 

 hydrothecai is very similar to that given in Hopkinson's 

 description of his D. Etheridgii] and the explanation of the 

 rounded knob-like form of their distal extremities may be 

 gathered from a study of fig. 27 b. The " inverted " denti- 

 cles in Hall's D. marcidus are simply the compressed and 

 prolonged oblique denticles that project from the outer sinus 

 of the excavations. 



The characteristics of this species are so unique that there 

 can be little doubt that it is worthy of generic rank. In the 

 general habit of the polypary, in the form of the hydrotheca, 

 and in the punctate character of the test, it differs both from 

 Diplograptus and Climacograptus. I would suggest for it 

 the generic title of Cryptograptus (Gr. Kpv%Tos, concealed), in 

 allusion to the intramarginal and usually concealed aperture 

 of the hydrotheca?. 



Cryptograptus, gen. nov. 



Gen. char. Polypary diprionidian, with attenuated punc- 

 tate test, subparallel margins, and concavo-convex (?) section. 

 Hydrotheca? inclined ; lower wall straight or slightly arcuate, 

 outer third forming a distinct excavation, the upper sinus of 

 which is mucronate and oblique ; outer wall very short, per- 

 pendicular ; aperture very oblique, lying wholly within the 

 ventral margin of the polypary. 



Type Diplograptus {Cryptograptus) tricornis, Carr. 



Forms belonging to this genus are not uncommon in the 

 Upper Arenig rocks of Skiddaw ; and examples referred by 

 myself to D. tricornis have been collected from the Lower 

 Llandeilo strata of Pembrokeshire. The form figured in 

 PI. V. fig. 28 a occurs in remarkable abundance in the Upper 

 Llandeilo beds of Radnor. Cryptograj)tus tricornis is very 

 numerous in the Glenkiln and Lower Hartfell shales of the 

 south of Scotland, together with the variety (?) D. Etheridgii, 

 Hopk., and other forms. I strongly suspect that the Arenig 

 species Climacograptus antennarius, Hall, and Diplograptus 

 Hopkinsoni, Nich., belong to the same group. If so, the 

 genus has already been recognized in America, Britain, and 



