PROETUS. 21 



Tail short, flat. Axis large, conical, very elevated, not quite reaching the 

 border, with six well-defined rings, each bearing a prominent tubercle in the centre, 

 and one or two obscure warts on the sides. Limb almost flat, with a shallow 

 depression running round within the border, which latter forms a small segment 

 of a circle, and is marked with one or two raised strige. Four or five indistinct 

 segments on limb, which reach quite to the border. 



Size of Head. — 11 mm. in length, 18 mm. in width, 6 mm. in depth. 



Size of Tail. — 8 mm. in length, 14 mm. in width, 4 mm. in depth. 



Localities. — This little species occurs at Lummaton, where it is commoner than 

 any other Trilobite, with the exception, perhaps, of Cyphaspis ocellata. A single 

 example from Wolborough is in Mr. Vicary's collection. 



Remarks. — Generally speaking the individuals of this species are of very small 

 size (Plate I, fig. 26) ; and, as a rule, the only part remaining is the detached 

 glabella, which frequently wants the outer layer of the test. In this condition the 

 surfaces of the glabella and the border are smooth. It is, however, easily recog- 

 nisable, and does not seem to vary to any appreciable extent. The flatness and 

 compactness of the head, and the extreme length of the neck-lobe are among its 

 most prominent features. The eye is large and long, being at least half the 

 length of the cheek, and is of a perfect kidney-shape and without the slightest 

 trace of lenses. The edge of the cheek is turned up round it in a short even fold 

 defined by the two furrows mentioned above. The cheek-spines seem to vary 

 considerably in length with age, as also does the obliquity of the neck. Remains 

 of the thorax or tail are very rare. One of Mr. Champernowne's specimens shows 

 a portion of the first thoracic segment, the axis of which is seen to be very wide 

 and covered with granules which are larger and more defined than those of the 

 head. It is with some hesitation that I refer the tails above described to this 

 species, but the pygidia of some species of Proetus described by Barrancle appear 

 to give reasons for so doing. I only know of three specimens, two in my 

 collection and one in the Torquay Museum ; and why they should be so much rarer 

 than the heads is difficult to explain. The more convex type of pygidium refer- 

 able to Proetus is decidedly more common at Lummaton, but there seems no 

 reason for doubting that these all belong to P. audax. On the other hand, in 

 several other Lummaton Trilobites the same rarity of the pygidium is observable. 

 Thus I know of only a single specimen of the tail of Cheirurus, only one of 

 Harpes, and none at all either of Cyphaspis or Lichas. 



Barrande describes thirty-five species of this genus from Bohemia, of which 

 twenty-four belong to his Etage F. To none of these can these species be 

 referred, and only two or three approach it at all nearly. It differs from all 

 (except P. Bohemicus) in having a small lateral tubercle or lobe between the 

 frontal lobe and neck, and in the extreme length of the neck-lobe. Moreover, in 



