402 CONTniBUTIONS TO MARINE BIONOMICS. 



III. The Systematic Features, Habits, and Respiratory 

 Phenomena of Portumnus nasutus (Latreille). 



The crab whose habits I now describe has not previously been 

 recorded as an inhabitant of Ihitish seas. I found two specimens, 

 both male, imbedded in a patch of coarse shell sand on the south side 

 of Drake's Island at low water, spring' tides: one on August 11th, 1896, 

 and the other on the following day. 



1. Nomenclature, 



My first impression on noticing this remarkable little crab 

 was that I had an abnormal specimen of a young Carcinus macncis 

 before me; but the possibility of such a leap from the normal as the 

 frontal area of this specimen would produce on a variation-chart 

 was soon disposed of by Trofessor Weldon, and we identified the crab 

 with the Portunus higuttatus of Eisso (1816), now usually known under 

 tlie name PJatyonicJms nasutus of Latreille (1825, p. 151; cf. also 

 Milne-Edwards, 1834; Costa, 1853, p. 11; Carus, 1885). 



The genus Platyonichus of Latreille (1818) was originally coextensive 

 with the genus PortummLs of Leach (1815), Latreille having simply 

 altered Leach's name owing to its similarity to the name Purlimus, 

 with which he feared it might be confused. Dana (1852), however, 

 and Bell (1853), showed that the species included within the genus 

 Platyoniclms were separable into two well-marked groups, which were 

 accordingly named by these writers Platyonichus and Portumnus 

 respectively, the latter name being reapplied to the group which 

 included Leach's type, viz., Portumnus latipes. It is to the latter 

 group that Platyonichus nasutus belongs, so that I must refer to it 

 for the future as Portumnus nasutus. 



It is true that the earliest specific name applied to the present species 

 is higuttatus of Risso (1816), the name nasutus of Latreille (1825) being 

 nearly ten years later. Since, however, the species has been invariably 

 referred to under Latreille's name, probably owing to the influence of 

 Milne-Edwards' adoption of it, I submit that we have here an ex- 

 ceptional case which demands exceptional treatment. The rule of 

 priority provides a decisive method of dealing with a confused and 

 complicated synonymy ; but its application in the present case could 

 not be urged on such grounds, and would be distinctly inconvenient. 

 I shall therefore adhere to the employment of Latreille's name nasutus 

 in referring to the species under discussion. In the event, however, 

 of possible differences being discovered between Mediterranean and 

 Atlantic races of this species, I would point out that liisso's name 



