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



abundance in the highest zones of the Glenkiln shales at 

 Glenkiln, Dobb's Linn, Carnalea (Ireland), and in the higher 

 Llandeilo rocks of Builth, at Wellfield, and near Builth-road 

 station, 



17. Dicellograptus jxztulosus, sp. now 

 (PI. V. figs. 18a-18/!) 



Branches of polypary stout and slightly curved, diverging 

 from each other at a wide angle. Axil short, rounded, or 

 obtusely angular ; axillary spine stout, oblique, often invisible ; 

 radicle well marked ; lateral spines rudimentary, rarely visible. 

 Hydrothecae twenty to twenty-two to the inch, free for a small 

 fraction of their length; distal portion contracted; aperture 

 very oblique, opening partly within a distinct excavation in 

 the base of the succeeding hydrotheca. 



In the majority of examples of the typical form of this 

 species the axillary portion is bluntly triangular in form, the 

 two primary hydrothecee being directed slightly backwards. 

 The proximal extremity is always provided with a well- 

 marked radicle ; but the lateral spines are only very rarely 

 distinguishable, and are always very rudimentary. The 

 sicular spine varies much in length, and is very frequently 

 invisible altogether. When present it is generally stout and 

 pointed ; it hardly ever occupies its normal position with 

 respect to the dorsal angle of the branches, but inclines to one 

 side and is occasionally united to the nearest branch by a 

 distinct membranous film. 



The hydrotheca? differ essentially from those characteristic 

 of the majority of the Dicellograpti in the fact that the distal 

 portion is not free and protuberant, with introverted extremity, 

 but is rather narrowed distally, and the aperture alone is ob- 

 lique and directed inwards. A very small fraction only of 

 the apertural margin lies outside the line of the ventral edge 

 of the polypary ; and hence the polypiferous border has a very 

 smooth appearance. The excavation is somewhat triangular 

 in form, and occupies from one fourth to one sixth of the 

 ventral margin. 



Dicellograptus patulosus differs from D. Forclihammeri in 

 the form of the axillary portion of the polypary, in the absence 

 of freedom and introversion of the distal fraction of the hydro- 

 thecas, &c. From all other species its general habit is suffi- 

 cient to distinguish it. 



Horizon and Locality. Occurs in great numbers in a single 

 zone in the Glenkiln shales at Glenkiln, Craigmichan, Dobb's 

 Linn, &c. ... 



