104 BULLETIN 138^ UNITED STATES NATIONAL MUSEUM 



spines stout, conical, blunt, directed obliquely distad, nine in each 

 row, diminishing in size toward tip of finger. Upper and lower sur- 

 faces (pi. 24, fig. 5 and 6) covered with large spaced granules, larger 

 at proximal end ; some of them show a hair-socket. Two low, pre- 

 hensile teeth, the basal one very large, subcircular, the next tooth 

 touching the first and much smaller, broader than long. Finger 

 slightly curved inward toward tip, prehensile surface hollowed out 

 in middle third. 



Wrist : The wrist belongs to a smaller cheliped than the dactylus. 

 Upper margin pronounced, armed with a single row of 15 spines 

 which increase in size toAvard distal end with exception of two small 

 spines on articulating condyle, and have on the outer side of each a 

 socket for hairs. Just below this row on the inner side and 

 nearly parallel but diverging a little distally, there is row of flattened 

 tubercles directed upward and with an elongate orifice in the top of 

 each. Further down the inner surface (pi. 24, fig. 8) is covered with 

 similar flattened, striated tubercles directed obliquely upward and 

 distad and equipped each with a similar orifice. On the lower, short 

 part and also on the distal part of this surface there are simple 

 oblique striations which terminate along the distal edge in a row of 

 granules. The ornamentation of this surface resembles a colony of 

 encrusting bryozoans. Outer surface (pi. 24, fig. 7) rougher, armed 

 with fifteen or more short, upstanding, conical spines or tubercles 

 each with a socket on upper side; the intervening space is filled with 

 granules, some of which also are provided with hair sockets. 



Measurements. — Length of right movable finger, holotype (a short 

 piece missing from either end), 7.3 mm. Length of right wrist, 

 paratype (chord of outer margin), 5.1 mm. 



Occurrence. — California: Rincon del Potrero, Santa Monica; 

 Pleistocene series; one left wrist or carpus of cheliped, paratype: 

 Cat. No. 353568, U.S.N.M. 



California : Deadman Island, southeast of San Pedro ; Pleistocene 

 series; one right movable finger or dactylus, holotype; in Stanford 

 University. 



Relation. — In shape the dactyl approaches that of D. impressus (de 

 Haan),*' but the ornamentation is very different, impressus having 

 four rows of acorn-shaped tubercles. While it is not certain that 

 wrist and hand belong to the same species, there is a strong proba- 

 bility that they do. Both have the Dardanus form, were found in the 

 same horizon and geographically not far apart. There is sufficient 

 similarity in their ornamentation. 



D. arnoldi is not akin to the Recent Californian species, D. jor- 

 dani.^'^ In D. suhaequalis, described above, the chelae are subequal 



*' Pagurua impressus de Haan, Fauna Japon., Crust., 1849, p. 207, pi. 49, fig. 3. 



" Schmitt, Univ. California Tubl. Zool., vol. 23, 1921, p. 126, pi. 17, figs. 3 and 4. 



