ILL^NUS. 



215 



same old land) will be worth searching for the fossils of the ' Arenig or Skiddaw group,' 

 for many years to come. 



Illcenus Bowmanni ? 

 {11. latus, M'Coy : Peeblesshire). 



To finish the description of this large genus, I may add figures of one or two doubtful 

 forms, respecting which some information is desirable. Two of them are referred to 

 at p. 186. 



Fig. 55 represents the original specimen of Prof. ^^^ ^5 



M'Coy's lllcBnus latus, from the Wrae limestone of Peebles- 

 shire. I regard it as only a pressed and shortened head 

 of //. Bowmanni, altered by cleavage action so as to de- 

 stroy the proportions. The glabella-furrows, however, are 

 rather shorter than usual ; and unless we bad the body 

 and tail, it would be ditficult to prove it to be that species. 



Locality. Bala Limestone ; Wrae quarry, Peeblesshire. 



Fig 56 is a figure of the species found in the true Llandeilo Limestone of Knock 

 dolian, Ayrshire. I should have little hesitation in describing it as //. crassicauda 

 which I have before said, p. 193, has never certainly yet 

 occurred in Britain ; but the greatly truncated angles of the tail 

 are sufficient to make me for the present quote it with doubt. 

 The shape of the tail is identical with that figured by Dr. 

 Volborth as the common Russian species, and the caudal fascia 

 is of a like breadth : it is very much broader than any British 

 species with which it can be compared, except //. Portlockii, 

 pi. xxvi, fig. 3 ; but the less breadth of the axis, and the 

 more remote fulcrum, as compared with that Caradoc species, are characters in which 

 it resembles //. crassicauda, which comes from Llandeilo rocks. 



Fig. 57 is a small imperfect head of a Bumastus from the Bala (or Hirnant ?) Lime- 

 stone near Chirk. It is a sohtary specimen, and only shows enough to 

 prevent our identifying it with either of the four species of Bumastus 

 figured in our plates. The head is not at all carinate, as in Bumast. 

 Maccallumi, pi. xxx, nor are there any glabella-furrows visible. But this 

 may be because we have here the outside crust, which we do not know 

 in the Ayrshire species. It is worth figuring, to incite collectors to 

 search for it in its locality, a prolific spot, and one which contains many 

 rare fossils. 



Locality. — Upper Bala (or Hirnant) Limestone of Mynydd Fron Frys, near Chirk 

 (presented to the Woodwardian Museum by the late Mr. Bowman in 1841). 



Illmnus crassicauda, Wahl. ? 



Llandeilo Limestone of Knock - 



dolian, Ayrshire. 



o 



//. {Bumastus), sj>. 



Mynydd Fron Frys, 



near Chirk. 



28 



