208 B GEOLOGICAL SURVEY OP CANADA. 



and its teeth are broad and in contact at their bases. The frontal and 

 hepatic regions and the anterior part of the branchial are smooth and 

 flat or concave, but there are three very high, wart-like prominences 

 on the gastric region, of which the two anterior are larger and mark 

 the protogastric lobes, while the smaller is in the median line and 

 behind them ; there are similar, but posteriorly less distinctly circum- 

 scribed protuberences on the posterior part of the branchial region ; 

 and the tops of all the protuberances are ornamented with smooth 

 mammillary granules, which are large anteriorly but gradually loose 

 the mammillary character in the rough and granular posterior regions 

 of the carapax, which differ much from the anterior and middle 

 regions, which are very smooth, except on the flattened summits of 

 the gastric protuberances just described. 



Telmessus serratus White. 



"White, Annals Mag. Nat. Hist., xvii., p. 497, 1846; Voyage of Samarang, 

 Crust., p. 14, pi. 3, 1848. — Dana, United States Exploring Expedition, 

 p. 303, pi. 18, fig. 8, 1852. 



There are three specimens of Telmessus from the Queen Charlotte 

 Islands : two small males, in alcohol, from shallow dredging, and a dry 

 and broken female much larger than the males. The female agrees 

 very well with White's figure and is about the same size as White's 

 specimen, though of the opposite sex. The larger of the two males 

 agrees with Dana's figure and description, except that the median 

 teeth of the front are not quite as acute and prominent, projecting 

 only very little beyond the lateral. The tooth forming the lateral 

 angle of the carapax is much more prominent than in the female. 

 The smaller male differs from the larger in having the antero-lateral 

 margins of the carapax nearly parallel, and the tooth forming the 

 lateral angle relatively even much more prominent than in the larger 

 male. These differences are shown in the following measurements of 

 the carapaces of the three specimens : — 



$ $ ¥ 



Length, including frontal spines 6-6 mm 20-3 66-5 



Breadth in front of lateral teeth 5-7 19-4 66-0 



Breadth, including lateral teeth 8-9 25-3 82-2 



The differences are apparently due to the age of the specimens, and 

 I think there can be little doubt that White's specimen and Dana's 

 were of the same species. Whether the T. cheiragonus described by 

 Tilesius and by Brandt, and T. acutidens Miers (ex Stimpson), are also 

 of the same species, I am uncertain. The synonymy in this genus is 

 still in great confusion, and the relations of the different forms can be 

 made out satisfactorily only by careful examination of a large series 

 of specimens. 



