616 ME. H. H. THOMAS ON NEW [Aug. I90O, 



32. Fossils in the Oxford University Museum, IV : Notes on some 

 undescribed Trilobites. By H. H. Thomas, Esq., B.A., F.G.S. 

 (Eead June 20th, 1900.) 



[Plates XXXTV & XXXV.] 



In the course of arrangement of the Trilobites in the Oxford 

 University Museum, a few forms came under notice which might be 

 considered worthy of description. They are two species of Dalmania 

 from the Wenlock Shales, and one of Olenus from the Shineton 

 Shales. 



Phacops {Dalmania) cobonatus, sp. nov. (PL XXXV, 

 figs. 1-4.) 



This species does not attain any considerable size, its total length 

 being from f- to |- inch, while the ratio of its greatest breadth to 

 length exclusive of the caudal spine is as 3 : 5. 



The head-shield is semicircular and moderately convex, the 

 genal angles being produced posteriorly into two long spines 

 extending to the sixth thoracic segment. The external border is a 

 flattened margin, narrowing in front of the glabella, and produced 

 on its external edge into a series of spines, seemingly sixteen in 

 number, symmetrically arranged. They are more or less equidistant 

 one from the other and are of the same length, excepting those two 

 that are immediately in front of the eyes, which seem to be about 

 twice the length of the others. 



The glabella is coarsely tubercular with smaller granules 

 interspersed, and it widens anteriorly to more than one-third of 

 the width of the head- shield. The forehead-lobe is more or less 

 rhomboidal in outline, its width however being greater than its 

 length, the latter being equal to half that of the total glabella. 

 The inferior lobes diminish in size posteriorly, being separated by 

 deep furrows which do not pass across the glabella, but are inter- 

 rupted by a well-marked ridge running back from the frontal lobe 

 to the posterior border. 



The axial and neck-furrows are deep, while the axial part of 

 the posterior border is furnished with a large central tubercle. 



The facial suture circumscribes the glabella at its anterior 

 margin, falling with an inward curve to the eye, and then arching 

 upward and outward from the lower angle of the same, cuts the 

 lateral border. The eyes are large and sharply curved, extending 

 from the basal furrow of the glabelJa to the middle of the anterior 

 inferior lobe. In no one of the specimens can the facets, however, 

 be seen. 



The thorax consists, as usual, of eleven segments, the axis 

 being but moderately convex. The pleurae are truncated and 

 grooved, their fulcra being so situated that the inner part of the 



