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Zoology* 121 



their having been made by successive steps, afforded by this succession 

 0? corresponding prints at regular intervals, is the strongest we possess. 



They are in pairs, and the pairs extend in two parallel linear series 



with a groove midway between the two series. The outer impression 

 of each pair is the largest, and it is a little behind the inner one. Both 

 are short and broad, with feeble indications of divisions at their fore 

 part. They succeed each other at intervals much shorter than that be- 

 tween the right and left pair. 



'^The median groove ivS well defined and slopes down more steeply 

 at its sides than towards the bottom, at some parts of the track. I con- 

 clude from these characters that the animal which left the track was a 

 quadruped, with the hind-feet larger and wider apart than the fore-feet ; 

 with both hind and fore-feet very short, or impeded by some other part 

 of the animal's structure from making any but short steps ; that the fore 

 and hind limbs were near each other, but that the limbs of the right and 

 those of the left side were wide apart; consequently, that the animal 

 had a short but broad trunk, supported on limbs either short or capable 

 only of short steps; and that its feet were rounded and stumpy, with- 

 out long claws. 



"As to the median impression, that may be due either to a thick 

 heavy tail, or to the under surface of the trunk, dragged along the 

 ground. The shape of the body and the nature of the iiinbs, indicated 

 by the above-described characters of the steps, accord best with those 

 of the land or freshwater tortoises, and the median groove might have 

 been scooped out by the hard surface of a prominent plastron. 



'^ The disproportion in the size of the fore and hind-feet is such as 

 we find in some existing Terrapenes, e. g., the Emys geograjjfncay 



III. Zoology. 



!• On ihe^ Classification of the Cancroidea ; by James D. Dana. 

 Ihe Cancroidea (or Crustacea Cyclometopa), like the Maioidea, are 

 characterized by having, (1) the branchia) 9 in number, 7 of which 

 lie so as to form the exterior of the branchial pyramid ; (2) the efferent 

 passage from the branchial cavity passing over the lateral portions of the 

 palate ; (3) the male genital orifices situated in the base of the posterior 

 ^gs and covered by the abdomen ; (3) the male abdomen not narrower 

 ^t base than the corresponding part of the sternum; (4) the buccal 

 ^ ^-''T ^^hquadrale, and the 4th joint of the outer maxillipeds articulated 



^vith the 3d by its inner angle. The Telphusidee have these characters, 



and may be considered true Cancroidea, though approximating to the 



rapsoidea in the large vacant space in the branchial cavity, and having 



some peculiarities in the branchice fitting them for fre'shwater life. 



i he Corystes group also partake of the Cancroid character ; yet they 



both^^^ U'^^ '^' ^" ^^^ '^'"S® ^^^^"^ antennae more or less hairy, and 

 Ih *^ respect and in form, they approach the Hippa group, and 



^8 have a much lower position in the series than the Cancroidea. 



J^y nave no true relation in the character of the buccal area and 

 enerent canal to the Leucosia group. 



it ] ./^"^^^ Acanthocyclus and Corystoides (of Lucas) have the gen- 

 ^^ orifices, sternum and abdomen, and outer maxillipeds of the Can- 



^ ea and Corystoidea ; but the branchise (in Acanthocyclus at least) 



SECOND StoTEs. Vol XII, No. 34.-^uly, 1851. 16 



