520 



MISS G. L. ELLES ON THE GEAPTOLITE [Aug. 1 898, 



and the other two are long spinous outgrowths from the bases of 

 thecae 1^ and 1^. These spines usually include between them an 

 angle of about 120°, or sometimes rather less ; they may be straight 

 or slightly curved, are usually rigid, and about ^ inch (8*7 mm.) 

 long. The rigidity and wider angle serve to distinguish them from 

 the similar outgrowths in Cryptograjptus Hojphinsoni. 



The thecae number between twenty-four and twenty-eight to the 

 inch(nine to eleven in 10 mm.), 



Pig. 31. — Cryptograptus antenna- 

 rius from Outerside and Mun- 



grisedcde, coll. J. E. Marr 



[Nat. size.] 



the virgula is usually prolonged 

 for about ^ inch (12'7 mm.) 

 or more beyond the distal 

 extremity of the rhabdosoma. 

 Two specimens show peculiar 

 features. In one, there ap- 

 pear to be two basal spines 

 on the left side of the rhab- 

 dosoma, the occurrence being 

 such as to suggest that a spine 

 proceeded from each of the 

 lower angles of the quadrate 

 basal cell. Whether this is 

 usually the case I am unable 



to say : I have observed it only in two specimens, and it may be 

 due to a process of exfoliation during preservation. 



In the other specimen the basal spines are four in number, two 

 on each side, and in addition to these there are other spines pro- 

 iecting from the side of the rhabdosoma at a point rather more than 

 halfway down its length. The spine on the left is clearly seen, 

 and that on the other side is indicated : both are directed obliquely 

 downwards. 



Whether this is merely an accidental occurrence I cannot say ; if 

 it should prove to be constant in some forms the variety might be 

 appropriately termed var. spinosus, but I incline to the belief that 

 it is merely a pathological variation. 



Occurrence. — On slabs with Didymograptus hifidiis, Upper 

 Skiddaw Slates. 



Localities. — Outerside ; Mungrisedale ; Glenderamakin Valley ; 

 Mosedale Beck, near Troutbeck : Bannerdale Pell. 



(a) Cryptogeapttjs Hopeinsoni (Mch.). 



1869. Diplograpsus SopMnsoni, Nich. Ann. Mag. Nat. Hist. ser. 4, vol. iv, p. 234 



& pi. si, fig. 7. 



The structure of this species, referred originally by Nicholson to 

 the genus Diplograptus, seems to be more in accordance with that 

 of Cryptograptus^ Lapw.^ Nicholson's type-specimen is in the 

 British Museum (Nat. Hist.) ; it occurs with Tetragraptus quadri- 

 hrachiatiis (Hall). There are also other specimens in the Wood- 

 wardian Museum. 



^ See Lapworth, Ann, Mag. Nat. Hist. ser. 5, vol. r (1880) p. 174. 



