1857.] HUXLEY — PYGOCEPHALUS COOPERI. 369 



among either tlie lower Becapoda or the Stomapoda* ; and supposing 

 the interpretation which I have given of this difficult fossil to be well 

 founded, it affords, so far as I am aware, the first certain evidence of 

 the existence of Podophthalmia at so early a period as the Carboni- 

 ferous epoch f. 



DESCRIPTION OF PLATE XIII. 



Fig. 1 a. Pygocephalus Cooperi, No, 1 : nat. size. The Manchester specimen. 

 Fig. 1 b. The same : magnified \^ diameter. 

 Fig. 1 c. Thoracic appendage of the same . niagntfied. 

 Fig. 2. Mr. Cooper's specimen, No. 3 : magnified. 

 Fig. 3. Mr. Cooper's specimen, No. 2 : magnified. 

 Fig. 4. Thoracic appendage of iWy«is : magnified. 

 Fig. 5. Antennule and antenna of Mysis : magnified. 



Fig. 6. Gonodactylus bent upon itself, in outline ; the appendages being omitted : 

 magnified. 



a. Quadrate disk. 



b. Central part of the body. 



c. Semicircular disk. 



d. Marginal portions of carapace. 



e. Tergal surface of abdominal somites. 



En. Endopodite. Ex. Exopodite. 



1'. Antennules. 



2'. Base and inner division of antenna. 



2". Outer division of antenna, or scale. 



* I have elsewhere (Lectures on General Natural History, * Med. Times and 

 Gazette,' May 23rd, 1857) given my reasons for limiting the group of Stomapoda 

 to Sf/ui/la and its immediate allies. The Schizopoda, including Mysis, are not 

 essentially different from Becapoda. 



t If the genus Gitocrangon, described by Richter (Beitrag zur Paliiontologie 

 des Thiiringer Waldes, p. 43), really constitute, as its discoverer considers, a trans- 

 ition between the Macrura and Brachyura, it is not only an earlier, but a more 

 highly organized Crustacean. 



3. On the Geology of Strath, Skye. By A. Geikie, Esq. 

 IVith Descriptions of some Fossils fi^om Skye ; by Dr. T. 

 Wright. 



(Communicated by Professor Ramsey, F.G.S.) 



[This paper will be published ' in the next Number of the 

 Journal.] 



