184 



SILURIAN TRILOBITES. 



somewhat trigonal, with the front a little produced, the sides flattened, and the hinder 

 angles much rounded. The head is very gibbous, a section of it across the eyes, as 

 shown in fig. 2, being a broad parabola. The principal gibbosity lies in this line, 

 about the base of the great eyes. These are closely appressed to the glabella, so as 

 to abut at their lower end on the short axal furrow, which is conspicuous here, but is not 

 carried further up. And the eyes are placed about half their length distant from the 

 posterior margin of the head. 



The course of the facial suture, below the eyes, is abruptly outward ; above them it 

 runs direct to the front margin, in a line continuous with that of the short axal furrows 

 before noticed. The cheeks are much flattened, and decline rapidly, and our figure 2a 

 rather too strongly expresses a marginal furrow within the angle — a character common 

 enough in other genera, but extremely rare in Illanus. 



The thorax, of only 8 rings, has a broad axis, which tapers backwards, and is gently 

 convex. The pleurae are not so wide as the axis ; they are flat as far as the fulcrum, 

 which is placed at one half in the hinder rings, and is pretty close to the axis in the front 

 ring ; thence they bend a very little downward and backward to the oblique tips. 



The tail is less than a semioval, and has the front edge straight. The axis is equal in 

 breadth to the sides, and reaches down three fourths the length of the tail ; it is rounded 

 at the tip, flattened above, and with a distinct furrow all round it. The tip is very little 

 prominent, but clearly defined by the prominence, as the sides of the axis also are by 

 the axal furrows. The Hmb is flat, as, indeed, the whole tail is ; and only the edge turns 

 gently downward. 



The relatives of this little species are clearly to be found in the Panderia^ triquetra 

 and P. minima described by Dr. Volborth in his paper in the 

 ' Transactions of the Imperial Academy of St. Petersburg,' vol. 

 vi, No. 2, 1863, pi. iii, figs. 13 — 19. One of these is given in our 

 woodcut, fig. 47. Though I think Panderia only a subgenus, it 

 is a very good and distinct one; and the eight body-rings, 

 with their tapering axis, the flattened caudal shield with its long 

 distinct axal lobe, and the large relative size of the head and 

 eyes, mark it as an embryonic form (not using this word in a 

 strict sense) of a comprehensive genus. Tlie figure of P. minima is 

 especially like ours in the gibbosity of the vertex, direct facial 

 III. {Panderia) triqnetru,,y^\o. guturc in frout, and approximated eyes; and it is about the same 



L. Silurian, N. Russia. . . . 



size. Still, it differs in nearly all its proportions from P. Lewisii. 

 Locality. — Caradoc or Bala limestone of Moelydd, Oswestry,— near Llanymynech 

 quarry (where "Fossils" is printed on the Ordnance Map). Cabinet of the Rev. D. P. Lewis). 



* Named in honour of the veteran naturalist Dr. Pander, so well known for his works on tbe fossils 

 of Russia. See foot-note, p, 180, for a reference to his discovery of the membranous feet of Trilobites. 



