18 CARBONIFEROUS TRILOBITES. 



General form an elongated oval ; head semicircular, glabella rounded ante- 

 riorly, the raised central portion marked by two short lateral furrows on each side, 

 and by the usual rounded basal lobes, surrounded in front of the eyes by a rather 

 broad, flat, circular border formed by the fixed cheek, which contracts behind the 

 eyes, but extends obliquely outwards on each side from the neck-lobe, which is 

 rather wider and more strongly marked than the succeeding free segments of the 

 thorax. 



Eyes moderately large, reniform, smooth, for, when the faceted surface is 

 visible, the lenses are very minute. Free cheeks terminating in an acute angle on 

 the anterior border, and elongated posteriorly into spines which reach to the fifth 

 thoracic somite. Raised portion of the cheek sparsely granulated, border smooth 

 and broad, under margin striated. The nine free thoracic somites are nearly 

 of equal size, the raised axis being slightly broader than its pleuree; the axis 

 smooth, pleuree very minutely granulated and bluntly terminated. 



Axis of pygidium composed of sixteen coalesced somites with four to five 

 granules in a row on each axial somite, about thirteen lateral ridges to the pygi- 

 dium with about six granules on each ; margin narrow, plain. 



Formation. — Carboniferous Limestone. 



Localities. — Bolland, Yorkshire ; Clithero, Lancashire ; Derbyshire ; Kildare ; 

 St. Doolagh, Co. Dublin ; Limerick, west of Dromore "Wood ; Hook Head, Wex- 

 ford ; and Little Island, Cork. 



It has been a source of no small anxiety to adjust the various claims of authors 

 to priority in the naming of this species. 



I was at first led astray by Prof. De Koninck, and, guided by him, had placed 

 P. gemmulifera, P. Kellii, and P. quadriserialls under P. pustulata. But upon 

 referring to Schlotheim's " Trilohites pustulatus'' (' Nachtrage zur Petrefact.,' 

 Gotha, 1823), I found not only that his figure could by no possibility be made to 

 accord with any Carboniferous Trilobite, but on referring to the text he states 

 that his specimen was derived *' aus dem jiingerem Uebergangs-Kalkstein von 

 der Eiffel ;" or from the newer Transition Limestone (Devonian). It is in fact 

 a pygidium of Phacops, or Dalmania. 



Dismissing then P. pustulata from the list, it was next necessary to consider 

 the rival merits of P. gemmulifera and P. Kellii to precedence. " AsapJtus gem- 

 muliferus^^ was the name given by Phillips to a pygidium in the " Gilbertson 

 Collection " from Settle, but his representation of it is not satisfactory, and it was 

 with pleasure that I turned to Portlock's figure and able description of P. Kellii, 

 based not on a pygidium alone (on which he asserts it is quite unsafe to make a 

 species) but upon an entire specimen. Here I felt at last was solid ground to rest 

 upon. But on looking carefully over the Gilbertson Collection I discovered the 

 original specimen, figured by Phillips as " A. gcmmuliferus.'' Now, this is readily 



