Naor! PROCEEDINGS OF THE NATIONAL MUSEUM. 229 
Japan. It is commonly taken with the seine on sandy shores, but often 
oceurs on gravelly beaches above low-water mark. In June the young, 
of half an inch to an inch in Jength, were much more abundant than 
adults, and were taken with the dredge in 4 fathoms weedy sand. 
In the time of Steller a species of Chetragonus was so abundant in 
Avatcha Bay (Kamschatka ) that it formed a common article of food 
among the inhabitants. At the present time, however, it has entirely 
or nearly disappeared, as we did not succeed in obtaining a specimen; 
nor do the naturalists of Beechey’s voyage mention having found it. 
ERIMACRUS, gen. noy. 
Carapace longer than broad, suboval; median lobe of the front cut 
into four teeth. Lateral margins arcuate, armed with seven teeth. The 
genital openings of the female occupy the posterior wall of a deep de- 
pression in the sternum, and are not covered by the abdomen, which is 
not concave on its margins between these openings. HKpistome with a 
straight upper margin. Basal article of antenna stout; a short wing- 
like extension fills the hiatus of the eye. Chelipeds long; ambulatory 
legs moderately long, spiny. 
Brandt considered this genus, or the species for which it is constructed, 
to be generically or subgenerically distinct from Platycorystes, but 
unfortunately gave it a name (Podacanthus) which had been used by 
Gray for a genus of Orthoptera. His other name, Platycorystes, was 
based on Telmessus cheiragonus as the type; therefore the name is not 
available. 
Erimacrus isenbeckii (Brandt). 
Plate xxvi, figs. 5, 6, and 7; plate xxvii. 
Platycorystes (Podacanthus) isenbeckit Brandt, Bwletin Physico-Mathématique de 
VAcad. de St. Pétersbourg, vol. vil, p. 179, 1848. Also in Middendorff’s Sibir- 
ische Reise, Band 11, Theil 1, p. 83, 1851. 
Cheiragonus isenbeckii Brandt, in postscript of the last work, p. 147. 
Brandt described this species under the heading ‘Genus vel sub- 
genus Platycorystes Sect. B (num subgenus proprium. Podacanthus?).” 
The collection contains over forty specimens, all from the Aleutian and 
seal islands, the habitat given by Brandt, who says that it is much 
rarer than cheiragonus. ‘Mertens obtained but one, and Wosnesenski 
only five, in eight years collecting.” 
Brandt described the front as kaving four teeth, no doubt counting 
the spines of the inner angles of the eyes, as in chetragonus, and says the 
middle pair are conspicuous. A large specimen before me has this 
appearance; the front is worn or broken until it shows but two central 
teeth. The young, however, have four small sharp teeth at this place, 
very closely like those of cheiragonus; the central pair are separated by 
the median sulcus; they are very brittle and in most specimens are 
broken off, leaving a straight margin between the outer pair broken only 
by the median suleus. Afterwards when these latter are broken off, as 
is the case with the large specimen, the median sulcus divides the pro- 
