Mr. O.Fisher — Changes of Latitude on the Earth's Surface. 291 



limbs succeeding it, are chelate, all the five pairs of legs being 

 monodactylous, as in Palinurus, Scijllarus, and Tlienus : but in this 

 division the carapace and the abdominal segments are not arched, 

 but expanded laterally ; whilst this Lias Crustacean, like the Astacid(e, 

 Palcemonidcs, etc., has the carapace compressed laterally, and the 

 segments of the abdomen are not flattened, but are well arched. 

 The antennules are not like those of Palinurus, which have a few 

 long articuli, but are multiarticulate like those of the Astacidce and 

 Faliemonidie. 



From a careful comparison, made in 1867, of its general characters, 

 I was led to consider the fossil before us as probably most near to 

 the recent genus Atya of Leach, from South ^ America, and 1 then 

 proposed to name it Frceatya scabrosa, but in all the recent species 

 of the genus Atya the third and fourth pairs of thoracic appendages 

 are modified so as to subserve, like the first and second pairs, rather 

 the office of maxillipeds or mouth-organs than of feet ; the fifth, 

 sixth, and seventh pairs alone remaining as simple monodactylous 

 ambulatory legs. Whether this modification of the third and fourth 

 pairs of thoracic appendages in the genus Atya has taken place 

 since Liassic times, and so the fossil form be really ancestrally 

 related to that modern crustacean, can only be a matter of con- 

 jecture, but bearing in mind this important difference in the modifi- 

 cation of the thoracic limbs, they have nevertheless still many 

 points of resemblance. I have therefore retained the original name 

 Prceatya (conferred upon it in 1867), and by that appellation I 

 now beg leave to introduce it to paleontologists and especially to 

 those who are interested in Liassic fossils. 



Explanation of Plate VII. 



Fig. 1. Frceatya scabrosa, H. "Woodw., Lower Lias, Barrow-on-Soar (drawn nat. 



size). The original specimen in the British Museum. 

 „ 2. Fraatya scabrosa, H. Woodw., Lower Lias, Bath. The original specimen 



in the Collection of Charles Moore, Esq., F.G.S., of Bath. 

 „ 3. Outline of Atya scabra. Leach (recent), South America. 



II. — On the Possibility of Changes in the Latitudes of 

 Places on the Earth's Surface ; being an Appeal to 

 Physicists. 



By 0. Fisher, CIL, M.A., F.G.S. 



MR. HILL'S paper in the June Number of the Magazine has 

 incited me to recur to the great question of the possibility 

 of changes in the earth's axis of rotation within itself. Mr. Hill is 

 well known to be an accomplished geologist ; but he writes as if he 

 were simply a physicist, without sympathies for the difficulties of 

 his brethren of the hammer. Yet we feel certain that such is not 

 the case. We know that he has stiadied in the field the tremendous 

 movements which the strata have undergone, being often compressed 

 into a small part of their original length : that he has appreciated 

 the almost ubiquitous presence, either in past or present time, of 

 Tolcanic activity : that he must feel how unsatisfactory all explana- 

 ^ Incorrectly marked as N. America on the Plate. 



