174 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



Strictly this description does not apply to the specimens ; but I suppose 

 the occipital furrow to be one of the three furrows mentioned, while the 

 *' posterior segment" terminating " in two obscure basal tubercles" can 

 apply to the slightly tuberculated extremities, and the small tubercles at 

 the extremities of the posterior lobes of the glabella. 



Fig. 33, is from a cast taken in a mould of the exterior surface, sliowiog the striations; 

 but the eye-lobes are not visible (figure enlarged}. 



Fig, 34, is from a cast of the interior in sandstone. 



Fig. 35, a profile of the same 



Fig. 36. An enlarged figure from a small head of this species. 



Fig. 37. A cheek of this species. 



Fig. 38. Profile or lateral view of the same. 



Fig. 39. A part of a thoracic segment. 



Fig. 40. A pygldium found associated with this species, the form of which corresponds 

 to the one figured by Dr. Owen, Tab. 1, f. 5. 



This species occurs in the greenish gray beds of Trempaleau and Mini- 

 sta, in the central portion of the series, associated with Ftijcha^pis mini- 

 scaensis ; and in gray beds a little lower in the series, associated with 

 Agnostus josepha, ConocephalUes ivisconsensis and C, anatinus. 



PTYCHASPIS (sp.?), 

 PLATE VI. FIG. 48. 



The figure ( Plate vi, fig. 48) is about three times enlarged, from a small 

 specimen which possesses the characteristics of ihm genus. 



It appears to be an entire head, but no facial suture or eye-tubercle can 

 be distinguished. It is possible that it may be the very young of P. mini- 

 scaensis, which, in all the smaller specimens, approaches the P. granulosa 

 in its appearance. With a single specimen, I hesitate to characterise it as 

 a distinct species. 



It occurs in the sandstone at Trempaleau, associated with P. granulosa 

 and Agnostus josepha. 



