Description of Genera and Species. 51 



Localities. — Liddel Water, New Castleton, and Glencartliolm, Langholm. 

 Horizon. — Cementstone group, Calciferous Sandstone Series. 

 Collector. — A. Macconochie. 



Perimectukus pattoni sp. nov. PL VI., fig. 9. 



1888. Pakesquilla j)attoni Peach, Trans. Geol. Soc. Glasgow, vol. viii, p. 173. 

 Nomen nudum. 



Specific Characters. — Length of specimen, 35 mm. Liteguments thin, smooth, and 

 unornamented. Form moderately long, stout, and applanated, and with only slight 

 taper of tail. Trunk measuring nearly one half of the length of the body. Epimera of 

 tail segments comparatively small. Body of t.elson comparatively short. 



General Description. — The integuments are so thin that the tail, except in the 

 firmer parts, is much wrinkled. The trunk, which measures nearly half the length of 

 the body, is seen to be curved upwards in the present specimen, carrying the carapace 

 with it. Tliis bend does not take place at the articulation in front of the last seven 

 segments as in the other cases where the carapace and head organs are bent down ; but 

 four of the seven segments share in the bend. The carapace seems to have been of the 

 usual form and without keels, but it is thin, and, being compressed against the under- 

 lying organs and having accidental wrinkles in addition, it is not easy to decipher. If 

 it possessed a rostrum it was probably detached before fossilisation, or else it is folded 

 down so as to be concealed ; for although a portion of the carapace has been broken 

 away, yet the position of the body of the mandible allows of the orientating of head parts 

 sufficiently to show where they might be expected to be seen were they present and 

 still attached. The last seven trunk segments forni complete rings as in the other 

 species, and the bend of the body already mentioned affords additional evidence of their 

 being comparatively free. The last two of these show plainly that the lappets of the 

 carapace overlapped their sides, only leaving the backs bare. The tail is particularly 

 massive and with little taper, forming as usual the greater part of the body. The first 

 six segments composing it increase slightly in length in backward succession. They are 

 all provided with epimera, which appear to be less deep than those *of the already 

 described species, and of slightly different form, being more rounded oil" at the anterior 

 angles and having hollowed out instead of straight inferior margins. They are 

 strengthened along the anterior and inferior margins Ijy the usual thicbmed band 

 ending in a spine, but there does not seem to be the same complete overlap on to each 

 other as in the other species, when the tail is fully extended as it is in the present case. 



