MUNIDOFSIS BAIRDII. 83 



connected from the latter genus in the absence of transitional species. Gula- 

 thodes, Ompliorrhjnclms, and Elasmonotus, on the contrary, are bound b}' a 

 perfectly graduated series of numerous connecting forms with the typical 

 species of 3Iicnidoj)sis.* 



In the large and plastic genus Munidopsis, evolution has progressed along 

 several lines of species, and for the purposes of a monographer it may be 

 useful to assign names to the extremes of modification found within the 

 limits of the genus, in order that the interrelations of the species may be 

 brought into view. This is the function, as I understand it, of the category 

 of classification known as subgenus, in which we see a genus in the process of 

 forming, as it were. By the more or less complete extinction of interme- 

 diate species we may assume that genera of the present have come from 

 subgenera of the past, and that future genera will be evolved from sub- 

 genera of the present. I would distinguish between genera and subgenera 

 much as the American ornithologists do between species and subspecies.! 

 Viewed in this light, subgenera may play a very useful part in a philosophi- 

 cal system of nomenclature. 



Munidopsis bairdii Smith. 



Galacantha bairdli Smith, Proc. U. S. Fish Comm. for 1SS2, p. 35G, 18S4. 



Munidopsis bairdii Smith, Proc. U. S. Nat. Mus., VII. 493, 18S1; Aim. Hep. U. S. Fisb Comm. for 

 1885, p. 649, Plate V. Fig. 2, 1886. 



Station 3381. 1772 fathoms. 1 male. 



Differs from the type, as described by Smith, as follows : the central pair 

 of spines of the gastric area and the anterior pair of spines of the cardiac area 

 are absent ; the rostrum has three spines on the right side, four on the left ; 

 the posterior margin of the cai'apace has three spines on the right side, two 

 on the left ; the body is slenderer. The differences are perhaps partly indi- 

 vidual, partly sexual. Smith's description and figure having been made from 

 a female specimen. 



* Professor Henderson in 1885 (Ann. Mag. Nat. Hist., 5tli Ser., XVI. 417) proposed the genus Galatliop- 

 sis as a refuge for certain species intermediate between Munidopsis and Elasmonotus. This only added to the 

 difficulty by drawing two arbitrary lines of division in place of one. In bis final report on the " Challenger " 

 Anomura, Henderson suppressed tlie genus Gulathopsis and assigned the intermediate species to Elasmonotus, 

 expressing at the same time bis grave doubts concerning the separability of Elasmonotus from Munidopsis 

 (Challenger Anomura, pp. 158, 165). It is of interest in this connection to note that Milne Edwards and Bou- 

 vier (op. cit., p. 283) incline to place these same species in Munidopsis rather than in Elasmonotus. 



t The Code of Nomenclature and Check-List of North American Birds adopted by the American Orni- 

 tbologists' Union, being the Report of the Committee of the Union on Classification and Nomenclature, p. 3). 

 New York, 1886. 



