New Species of Trilobites. 377 



row neck-like central lobe, and the depth of the dorsal furrows. 

 The eye is depressed conical or sub-globular, and very like that 

 of I. Conradi; the space between it and the dorsal furrow tumid 

 and one-third wider than the central lobe. The front margin of 

 the head is somewhat straight, a little convex along the middle, 

 and slightly concave in front of the eye. The lateral extremities 

 of the head are sharp and nearly in a line with the front margin. 

 The posterior margin is strongly t.ri-lobed by the dorsal furrows, 

 which are at first sub-parallel or gently diverging as far as the 

 level of the eye ,when they curve outwards, and become obsolete; 

 in the cast they are distinctly marked nearly to the front margin. 

 From the eye the posterior margin is straight and extends out- 

 wards and forward to the lateral angles, which are nearly on a 

 line with the front margin. The head is abruptly elevated in 

 front ; the central lobe a little more elevated than the tumid 

 space on each side between the dorsal furrow and the eye, but 

 about the centre of the head it is flattened or very depressed 

 convex, a character which distinguishes this species from I. coni- 

 frons. The facial suture I have not made out. The eye is 

 distant half its own width from the posterior margin, and from 

 the dorsal furrow a distance equal to once and a hird the width 

 of the middle lobe. In a specimen where the width of the head 

 between the two lateral angles is eight lines, the length is three 

 lines and a half, and the width of the dorsal lobe one line and 

 three-fourths. 



Em. 10. 



Fig. 10. — Mantis an%usticollis. a Back part of the head. 6 Front. 

 c Oblique view of one side to shew the pointed front angle. 

 d Side view. 



The central lobe is finely and closely punctured, the punctures 

 just visible to the naked eye and nearly in contact with each 

 other. The remainder of the head is smooth. 



Allied to I. Conradi, but in that species the width of the mid- 

 dle lobe is nearly twice the distance between the eye and the 

 dorsal furrow, while in this the distance of the eye is one-third 

 greater than the width of the lobe. 



