Mr. C. Lapworth en new British Graptolites. 161 



Dicellograptus complanatus appears to be confined to a 

 single horizon in the Moffat series. It occurs in extraor- 

 dinary abundance in a thin seam of dark shales near the base 

 of the " Barren mudstone " of the Upper Hartfell shales at 

 Dobb's Linn, Moory Syke, &c. It is met with upon the same 

 horizon near Portpatrick, and swarms abundantly in the cor- 

 responding zone in the Hartfell shales of county Down 

 (Swanston) , and in the equivalent Myoch-Bay beds of the 

 Bala rocks of the neighbourhood of Girvan. 



16. Dicellograptus intortus, sp. nov. 

 (PI. V. figs. 19a-19c.) 



Branches of polypary slender and gently curved, diverging 

 from each other at a very small angle. Axil pointed, pro- 

 vided with a strong radicle, but destitute of both sicular and 

 lateral spines. Hydrothecse twenty-four to twenty-eight to 

 the inch, free for one third to one half their length ; free por- 

 tion strongly introverted, opening within a deep and very 

 oblique excavation. 



The branches of the polypary in this species rarely exceed 

 one fortieth of an inch in average diameter ; they diverge 

 from each other at an original angle of about 30°, and gradu- 

 ally curve round in such a manner as to become first parallel, 

 then crossing. The point where they cross each other lies 

 generally within an inch or an inch and a half from the 

 initial extremity of the polypary. Many examples, however, 

 show no tendency to a crossing of the branches, but retain 

 their original angle of divergence throughout the whole of 

 their extent, which rarely surpasses three inches. 



The axil in this form is narrower than in any other species 

 of Dicellograptus yet described. There is no trace of a sicular 

 spine, and very rarely of lateral spurs. A well-marked radicle 

 is invariably present. 



The hydrotheca? are of the general type of those in Dicello- 

 graptus elegans (Can*.). They are short and stout, and the 

 free portion is strongly introverted. The excavation is rarely 

 discernible, being so completely filled by the introverted 

 theca, that even on the best-preserved examples it is only 

 visible as a very oblique slit traversing a large fraction of the 

 width of the polypary. 



This species has some little resemblance to Dicellograptus 

 caduceuS) Lapw., in its general appearance. The form of the 

 axil and its ornaments and the characteristics of the hydro- 

 thecse, however, are very distinctive. 



Horizon and Locality. Dicellograptus intortus occurs in 



