1922.] S. Kemp : Notes on Crustacea Decapoda. 287 



ADDENDUM. 



Prof. Ch. Gravier has recently sent me for examination a 

 number of Macrura from the Gulf of California collected by M. L. 

 Diguet. Among them I find two species of Pontonia which I 

 identify as Pontonia margarita Smith ' and Pontonia pinnae Lock- 

 ington* (nee Ortmann). Of the former there are numerous speci- 

 mens, obtained " dans l'huitre perliere " ; of the latter a single 

 pair obtained in Pinna rugosa. 



Miss Rathbun, 8 when describing Pontonia calif or niensis 

 remarks. — " This is the only Pontonia described from the west 

 coast of North America, the P. margarita of Smith being a Con- 

 chodytes." These statements call for correction, for P. margarita 

 is in my opinion correctly placed in the genus Pontonia and P. 

 pinnae was recorded by Lockington in 1879 from the Gulf of 

 California.- Schmitt, 4 in his valuable treatise on Californian Deca- 

 poda mentions only P. calif or niensis and Borradaile, 5 who also 

 appears to have overlooked Lockington's species, follows Miss 

 Rathbun in referring P. margarita to the genus Conchodytes, 



In P. margarita the dactylus of the last three legs is broader 

 than usual, with the two claws strongly curved ; it thus bears a 

 strong resemblance to Conchodytes but lacks the large basal process 

 which is characteristic of that genus. 



P. margarita and P. pinnae are closely allied forms, but may 

 he distinguished by the following characters : — 



P. margarita Smith. 



Basal breadth of rostrum about half its 

 length. 



Eyes larger, almost reaching antennal 

 spine when extended laterally. 



Large chela with palm scarcely more 

 than one and a half times as long as 

 broad. 



Dactylus of last three legs very broad, 

 with accessory claw strongly curved 

 and directed slightly backwards. 



Spines on dorsum of telson large; pos- 

 terior pair almost equidistant between 

 anterior pair and apex. 



Size smaller, 20-28 mm. 



Lives in Margaritophora fimbriata. 



P. pinnae Lockington. 



Basal breadth of rostrum about equal 

 to its length. 



Eyes smaller, not nearly reaching an- 

 tennal spine when extended laterally. 



Large chela with palm twice as long as 

 broad. 



Dactylus of last three legs less broad 

 with accessory claw almost straight 

 and directed obliquely forwards- 



Spines on dorsum of telson small ; pos- 

 terior pair much nearer to apex than 

 to anterior pair. 



Size larger, 36-42 mm. 



Lives in Pinna rugosa. 



In the specimens of P. pinnae which I have examined the 

 carapace is much'more strongly arched in lateral view than in P. 

 margarita and in the ovigerous female the rostrum projects down- 

 wards at an angle of 45 . 



P. calif or niensis Rathbun, which I have not seen, appears to 

 be easily distinguished from both the above species by the very 



1 Smith, in Verrill, American Naturalist 111, p. 245 (1869). 



2 Lockington, Bull. Essex Inst. X, p. 163 (1879). 



8 Rathbun, Harrintan Alaska Exped*. X, p. 34 (1904). 



* Schmitt, Univ. Calif. PubL, Zool. XXII I, P- 38 (1921). 



6 Borradaile, Trans. Li int. Soc. (?.) Zool. XVII, p. 394. 



