176 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



in the proximal portion. The merus also recurves in its insertion into the 

 ischium, the inner border of which is spinate. For the corresponding con- 

 ditions in T. galapagensis refer to the description of that species. 



The use of the inwardly projecting comb on the rostrum remained a 

 mystery until a specimen from Acapulco, obtained by E. Yale Dawson 

 from among Viva, showed that the stem of the mushroom-shaped plant, 

 after being anchored in the hooked hairs at the base of the rostrum, had 

 been led forward between the rostral horns and under the almost touch- 

 ing projections, being thus firmly held in place. 



Tyche clarionensis, new species 

 Plate J, Fig. 5 



Type: Male holotype, A.H.F. No. 344, from off Sulphur Bay, 

 Clarion Island, Mexico, 30 fathoms, June 11, 1934, collected by Allan 

 Hancock Summer Cruise of 1934 at Velero III station 303-34. One male 

 and one female, paratypes, same station and date. For additional material, 

 see Material examined below. 



Measurements: Male holotype: length 20.6 mm, length posterior to 

 gastric tubercle 11.3 mm, width 13.6 mm, rostrum 3.0 mm, width 4.0 

 mm, cheliped 20.0 mm, chela 9.4 mm, dactyl 4.4 mm, height of palm 

 3.8 mm, ambulatory legs 26.5, 18.7, 14.5, and 11.3 mm, respectively. 

 Female paratype: length 12.1 mm, width 8.0 mm. 



Diagnosis: Rostral horns exceeding preorbital, broadly triangular. 

 Width of posterior medallion appreciably exceeding length. External 

 maxilliped somewhat inflated, groove lodging recurving projection of 

 exognath restricted to basal portion of ischium, anteroexternal angle of 

 merus produced into a thin blade. First free antennal segment cylindrical, 

 a spine at anteroexternal angle of basal article. Male first pleopod with a 

 square-cut flap protecting orifice and a row of papillae on concave margin. 



Description: Carapace broadened anteriorly, gastric and cardiac re- 

 gions elevated, branchial and hepatic regions depressed, the latter two 

 separated from each other by a sharp ridge extending diagonally back- 

 ward from the gastric prominence and with it delimiting anteriorly a 

 posterior medallion roughly hexagonal in shape. Of the four conspicuous 

 horns comprising the anterior portion of the carapace, the median or 

 rostral pair more advanced than the lateral or preorbital pair, the latter 

 inclined upward as well as outward and lying at a higher level. Rostral 

 horns not large, horizontal, broadly triangular, deeply cleft, and pro- 

 vided with a median protuberance on inner margins. Preorbital spines 

 directed more strongly forward than outward, tips acutely pointed, inner 



