174 SILURIAN TRILOBITES. 



LocaIify.—CAYiAT)oc? Black shales of Mount Pleasant, Carmarthen. 

 Presented to the Geol, Soc. Museum by Sir R. I. Miu'chison. It is named after 

 Lady Murchison, and is as rare a species as any in Britain. 



Stygina — , sp. Woodcut 40. - 



I do not like to risk naming an apparently new Stygina, with much shorter tail than 

 in the two preceding species. It is from the Caradoc slates of Pem- 

 40. brokeshire. The axis reaches only half way down the tail, and the 

 general shape is very broad, 



^^ .^^ ^ Locality. — Caradoc. Sholes Hook, Haverfordwest. Mr. H. Wyatt 



Edgell's cabinet. 



Stygina? Musheni, n, sp. PI. XXIX, fig. 1. 



S. major, triuncialis, late ovalis, suhplanus^ thorace caudd obtusd hreviore. Axis 

 corporis dejjressus, annulis arcuatis. Pleura lente convexa. Cauda semiovalis, obtusa [laf. 

 20 tin., lony. 14 lin.), axe longo primitm conico, dein parallelo ; apice hand prominulo, annulis 

 obscuris. Limbus lente convexus, margine angusto concavo. 



A larger species than either of the two preceding, and unfortunately not perfect 

 enough to determine the genus. I have figured it with the Illceni only because 

 there was most room on the plate. But it can hardly belong to any known British 

 genera except Asaphus or Stygina, and I refer it to the latter for choice. 



The whole fossil must have been above three inches long, for without the head it 

 measures fully two inches. The thorax, with a gently convex surface, is shorter than the 

 tail, and has a much wider axis, of eight arched rings, and with the axal furrows well 

 marked out. The pleurae are so much lost and obscured by rubbing, that we can only 

 see they were unfurrowed and much arched, not bent down greatly. This is like Stygina 

 or Illcenus, not at all like Asajjhus. 



The tail is more perfect, and shows a wide semioval plate, blunt behind, gently 

 convex, except the narrow concave border. The axis is not convex, and is very narrow, 

 broadest and conical at the base, then parallel-sided, and extending to the edge of the 

 concave border, but there indistinct, and, as it were, connate with the border. This is 

 partly the case with S. latifrons. A few obscure annuli show at the upper part. The 

 sides of the tail are smooth, and show no trace of furrows, not even the top one. 



Locality. — In a gray calcareous flagstone boulder (from the Caradoc probably) in 

 the drift of the Severn, near Buildwas. Cabinet of the late James Mushen, of Birming- 

 ham, whose persevering labours collected so fine a series of Silurian fossils. 



