﻿STAUROCEPIIALUS. 



87 



sulcata, recta, apicibus abricpfe recurvis. Cauda lata brevis, axe appendiculato, pleuris 

 primariis latissimis spatula/ is, margine postico truncato. 



In the absence of a figure sufficiently complete (for the one quoted above is very 

 defective) it is necessary to give a rather full diagnosis of this remarkable form, which 

 tends to show the passage of the Cheirurid into the Acidaspid family. Indeed, if Prof. 

 Thomson be correct in figuring 12 segments to the body, the species is abnormal for 

 either Acidaspis or Staurocephalus. The shape of the head shows clearly enough that it 

 is to Staurocephalus, or else to one of the sections of Cheirurus, that this bizarre fossil 

 must be referred. Cheirurus often has 12 segments, Acidaspis 9 or 10, Staurocephalus 

 only 10. The grooved pleura? are unlike Staurocephalus, but like the section Eccoptochilc 

 among the genus Cheirurus. But no Cheirurus has so clavate a glabella, though a 

 tendency towards it is exhibited in some species, and Spharocoryphe of Angelin is very 

 near to our fossil. There is an evident relation, too, with Lichas in this form, both in 

 the shape of the tail and the character of the pleurae. But the external position of the 

 facial suture — far up the cheek- — easily distinguishes it from that genus. I do not further 

 describe it, as it has already been fully noticed, though not figured, in Decade 11 of 

 the Geological Survey, just published. 



Locality.— Caradoc Schists, at the base of the " Orthoceratite and Graptolite Flags," 

 Penwhapple Glen, Ayrshire (Wyv. Thomson). 



Staurocephalus. Sp. PI. VII, fig. 25. 



An imperfect fossil, but distinct from S. unicus. It has tuberculate pleurae. 

 Locality. — Caradoc. Ayrshire (Prof. Thomson's cabinet). 



Deiphon, Barrande. 1850. 



Dciphon, the most abnormal in appearance of the whole Cheirurid family, is not 

 found, when closely examined, to depart very much from the ordinary type. Except in 

 the extreme reduction of the cheeks, and inflation of the glabella, the head might well 

 pass for that of a Cheirurus of the section Actinopeltis ; while the body and tail, extravagant 

 as they seem at first, have all the usual characters of the family. We have now perfect 

 specimens, and can improve Barrande's description. 



Form somewhat circular; very loosely built, and produced into spines on the margin. 

 The head composed of a globular glabella without furrows, long-spinous fixed cheeks, 

 and minute free cheeks, — the facial suture ending on the exterior margin. The eye pro- 

 minent, not stalked. Hypostome narrow, granular, without any rostral shield. Labrum 

 hexagonal, with a truncate end, small lateral auricles, and an unfurrowed hemispherical 

 centre ; the base is narrow and arched. Thorax of ten joints with a very convex axis, 



