CANCRID.E 47 



(Cancer amphioetus Rathbun.) 



Trichocarcinus dentatus Miers, Proc. Zool. Soc. London, 34, 1879. 

 Cancer amphioetus Rathbun, Proc. U. S. Nat. Mus., xxi, 582, 1898.— Rathbun, H. A. 

 E., X, 17s, 1904, and synonymy. 



No specimens of this species are in the University collection. Its 

 range on the Pacific coast — Magdalena Bay to San Diego Bay — and its 

 occurrence in Japan, make it at least possible that it will be found farther 

 north, as has proved the case with gihhosulus, and I have included it in 

 the keys for completeness. 



Cancer antennarius Stimpson. ^ 



Plate X, fig. 31. Plate XI, fig. 32. 



Cancer antennarius Stimpson, Proc. Calif. Acad. Sci., i, 88, 1856. — Holmes, Occas. 

 Papers Calif. Acad. Sci., vii, 49, 1900, and synonymy. — Rathbun, H. A. E., x, 

 176, 1904. 



This is one of the largest and most common crabs along shore at 

 Pacific Grove and is represented by numerous specimens ranging in width 

 from less than 10 mm. to 120 mm. 



There is considerable variation in this species and apparently a 

 tendency toward two types, the extremes of which might readily be taken 

 as separate species. By far the greater number — which I would consider 

 typical antennarius — have a smooth carapace devoid of hair except in the 

 very young — 15 mm. and less in width — where there are a few coarse 

 hairs. A small number show a tendency toward hairiness and roughness 

 of the hand, the extreme type of which, represented by a young female 

 measuring 46 by 50 mm., is shown in figure 32, PI. XI. In this the whole 

 carapace is densely pubescent (typical specimens of half the size show a 

 perfectly bare carapace) and on the summits of the areolations, which are 

 more marked than in the typical form, there are bunches of larger and 

 stouter hairs. The granulations on these elevations are coarser than on 

 the rest of the carapace and in some cases pass into small spines. The 

 antero-lateral teeth do not differ markedly from the typical form except 

 in being more thickened and in having the teeth spiny pointed. The 

 frontal teeth are more acute and thicker than is common in antennarius, 

 especially those lying on either side of the median tooth. The tips of 

 the basal joint and of the adjoining tooth on the lower orbital margin are 

 more acute than in typical antennarius of the same size. 



