168 



SILURIAN TRILOBITES. 



Other Species of the Subgenus. 



To render our account complete, I must quote from the Decade XI, Geol. Survey, 

 hoping in an Appendix to fill up these desiderata. 



AsAPHUs (IsoTELUs), n. sp. Salter. Quart. Geol. Journ., Vol. VII, PI. VIII, fig. 2. 



A caudal portion of an undetermined species, figured by myself for Sir R. I. 

 Miu'chison's paper on the Silurian rocks of the South of Scotland. Probably distinct 

 from /. gigas. 



Locality. — Llandeilo Flags (?). Bogang or Bugan, KnockdoHan, Ayrshire. 



AsAPHUS (IsoTELUS ?), sp. Salter. Quart. Geol. Journ., Vol. IV, p. 205. 



Quoted in Professor Nicol's paper on the Peebleshire Silurians. The specimen is 

 now lost, but was stated to be alhed to A. gigas. 



Locality. — Caradoc. Wrac limestone, Peeblesshire. 



Cryptonymus, Eichvald, 182.5. 



The typical species of this section is the well-known Asaphus expansus of the Swedish 

 and Russian works, of which a figure is given below. But though our British species 

 does not show the lobes of the glabella, it has the hourglass-shape of that portion ; the 

 facial suture in a low ogive close to the contracted front margin ; and the tail-axis with 

 many obscure joints marked out within the crust. Lest, however, I may be mistaken 

 in referring it to that subgenus, the figure will show what the type should be. I regard 

 the British fossil as a link between Cryptonymus and Isotelus. 



Fig. 37. 



Asaphus {Cryptonymus) expansus, Russian variety. Lower Silurian, N. Russia. Mus. Brit. 



