150 BULLETIN 152, UNITED STATES NATIONAL MUSEUM 



Genus TELMESSUS White 

 HORSE CRABS 



Cheiragone? Latreille, Fam. Nat., 1825, p. 270. 



Cheiragonusf Berthold, Latreille's Nat. Fam. Thierreichs, 1827, p. 256; nomen 



nudum. 

 Telmessus White, Ann. Mag. Nat. Hi.st., vol. 17, 1846, p. 497; type, T. serratus 



White.— Benedict, Proc. U. S. Nat. Mus., vol. 15, 1892, p. 223, and 



synonymy. • 



Plalycorystes Brandt, Bull. Phys.-Math. Acad. St. Petersbourg, vol. 7, 1848, 



p. 179; type, P. ambiguus Brandt. 

 Cheiragonus Brandt, Middendorff's Sibirische Reise, vol. 2, Zool. pt. 1, 1851, p. 



147; type, C. hippocarcmoides Brandt. 



Carapace broader than long, pentagonal. Lateral margins dentate. 

 Front between the antennae projecting, its anterior edge cut into four 

 small denticles. A broad tooth at inner angle of orbit. Basal 

 article of antenna short, broad and flattened; a triangular winglike 

 projection from it fills the inner hiatus of the orbit. Epistome with 

 a triangular point extending forward on the median line between the 

 antennules. Chelipeds short; ambulatory legs moderately long. 

 Sternum of female thickened and sculptured around the genital 

 openings; lateral margins of sixth abdominal segment broadh^ incised 

 leaving the openings fully exposed. Abdomen of male narrow 

 triangular from the fourth segment to tip. 



California to Bering Sea; Siberia to Japan. 



TELMESSUS CHEIRAGONUS (Tilesius) 



Cancer cheiragonus Tilesius, Mem. Acad. Imper. Sci. St. Petersbourg, vol. 5, 



1812 (1815), p. 347, pi. 7, fig. 1 (type-locality, Awatscha, Kamchatka; type, 



Mus. St. Petersburg [Leningrad]). 

 Telmessus serratus White, Ann. Nat. Hist., vol. 17, 1846, p. 497 (type-locality, 



not given; type in Brit. Mus.); List Crust. Brit. Mus., 1847, p. 124. 

 Plalycorystes ambiguus Brandt, Bull. Phys.-Math. Acad. St. Petersbourg, vol. 7. 



1848, p. 179 (type-localities, Okhotsk Sea, Kamchatka, and Aleutian Islands, 



Alaska; types, Mus. St. Petersbourg [Leningrad]). 

 Plalycorystes cheiragonus Brandt, Middendorff's Sibirische Reiso, vol. 2, pt. 1, 



1851, p. 85. 

 Cheiragonus hippocarcinoides Brandt, Middendorff's Sibirische Reise, vol. 2, 



part 1, 1851, p. 147; substituted for Plalycorystes cheiragonus. — Stimpson, 



Boston Journ. Nat. Hist., vol. 6, 1857, p. 465. 

 Telmessus cheiragonus Benedict, Proc. U. S. Nat. Mus., vol. 15, 1892, p. 224, 



pi. 25, pi. 26, figs. 2-4. — Rathbun, Harriman Alaska E.xpcd., vol. 10, 1904, 



p. 179. 

 Cheiragonus cheiragonus Ortmann, Zool. Jahrb., Syst., vol. 7, 1894, p. 420. 

 Telemessus cheiragonus Holmes, Occas. Papers California Acad. Sci., vol. 7, 1900, 



p. 69, and synonymy. 



Diagnosis. — Carapace broader than long. Epistome produced to 

 a point on the median line. Lateral margins of sixth segment of 

 female abdomen deeply incised. Lateral teeth of carapace six. 



Description. — Surface of carapace set with large granules, forming 

 lines in the posterior regions ; from the granules arise numerous short 



