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ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL.21 



oms, Albatross (Rathbun, 1893a, 1898) ; Arena Bank, 45 fathoms, and 

 San Lucas Bay, 6-20 fathoms, Zaca (Crane). Panama: Panama Bay, 

 51.5 fathoms, Albatross (Rathbun, 1898). Ecuador: Daphne Minor, 

 Barrington, and Hood Islands, Galapagos Islands, 9-80 fathoms, Velero 

 III (Garth, 1946) ; off Esmeraldas, 36-54 m, Askoy (Garth, 1948). 



Atlantic analogue: Mesorhoea sexspinosa Stimpson. 



Diagnosis: Four triangular carapace spines: one gastric, one cardiac, 

 and two at the end of each sinuous branchial ridge. A denticle at mid- 

 point of branchial ridge, in advance of this always a cluster of granules. 

 Front short, hairy. A sharp spine at base of cheliped ventrally. A spherical 

 tooth at base of movable finger. Male first pleopod short, stout, cylindri- 

 cal, constricted before contorted, bifid tip; lip of groove plumosely 

 setose, fine pubescence elsewhere. Male second pleopod three-fourths the 

 length of first, slender, reflexed, tip corneous, acutely pointed; subter- 

 minal concavity denticulate. 



Description: This species . . . distinguished by the globular form 

 of its carapace, the anterolateral portions swollen instead of depressed. 

 Gastric protuberance little elevated ; that of the cardiac region, on the 

 contrary, high and slender. Anterior branchial lobe bearing one or two 

 tubercles, lacking in [M. sexspinosa]. Posterolateral angles greatly ad- 

 vanced. Indentations of the anterolateral margin more distinct than 

 usual. Front scarcely surpassing the eyes and continuing the regular 

 curve of the carapace. 



Chelipeds strong. Hand armed above with a crest of ten triangular 

 teeth ; its external margin and its inferior margin cut into twelve or 

 thirteen tuberculiform teeth. Various surfaces of the hand smooth. 

 Sternum concave in front and devoid of tubercles. (A. Milne Edwards) 



Basal antennal [article] with a long trigonal spine below. Ischium of 

 external maxillipeds punctate, outer margin pubescent, inner margin 

 crenulate; merus with surface uneven, pubescent, anterior margin con- 

 cave ; a groove running diagonally forward and outward across the sur- 

 face; two tubercles on the outside of this groove . . . the inner angle 

 strongly produced and bearing a granular ridge. 



Male abdomen with first segment very short; second widest with a 

 transverse denticulate crest, having a larger denticle at the extremities 

 and in the middle ; third, fourth, and fifth segments anchylosed ; sixth 

 wider than long; seventh very short, triangular. Female abdomen with 

 seven segments; first segment almost concealed under the carapace; sec- 

 ond with transverse denticulate crest ; third with a similar faint crest not 

 continued to the margins. (Rathbun, 1893a, modified, of M. gilli) 



