Ii6 ANNALS OF SCOTTISH NATURAL HISTORY 



have already been mentioned in published catalogues of the marine 

 fauna of the Firth of Forth. These two species of Cirripeds, though 

 widely distributed, and from time to time brought to our shores 

 adhering to ships' sides, as well as by floating wreckage, etc., are 

 scarcely entitled to rank as members of our fauna. 



The Copepods are Harpacticns, sp., and Idya minor, T. and A. 

 Scott. The Harpacticus resembles a form described by me from 

 the Firth of Forth under the name of Harpacticus obscurus. Idya 

 minor has been obtained in the Clyde, but I do not know of any 

 previous record of it from the Forth estuary. 



The single species of the Isopoda observed belongs to Ncesa, 

 and agrees generally with Nizsa bidentata (Adams). The only 

 specimen observed was a male, the sixth segment of the peraeon 

 being produced backwards into a bidentate process. This species 

 has been recorded from the Clyde by the late Dr. Robertson of 

 Millport, but it does not appear to have been obtained in the 

 Forth. Ncesa is sometimes found inside the shells of dead Balani, 

 and in such circumstances may easily escape notice. This Isopod 

 appears to vary considerably in form, either from age or sexually. 

 The Rev. T. R. R. Stebbing, in his " History of Recent Crustacea," 

 says it "seems not improbable that the species named Dynamene 

 rubra and Dynamene viridis by Leach, and Campecopea versicolor 

 by Rathke, may represent the female, and Dynamene Montagui the 

 young male, of Ncesa bidentata" 



The Amphipoda comprise Stenothoe (f) monoculodes (Mont.), 

 Podocents falcatus (Mont.), and Caprella equilibra, Say. The 

 Stenothoe appears to agree perfectly with the species named, 

 except that the telson has two or three small spines on each side 

 near the margin, as in Stenothoe marina ; usually the telson of 

 Stenothoe monoculodes is unarmed. Podocerus falcatus was repre- 

 sented by both males and females; a few of the males had the 

 gnathopods fully developed, but the greater part of them were more 

 or less immature. Both this species and Stenothoe monoculodes have 

 already been recorded from the Firth of Forth. The Caprella 

 equilibra, though a member of the British fauna, has not hitherto 

 been recorded from either the Firth of Forth or the Firth of Clyde. 

 Most of the specimens obtained were immature, and differed con- 

 siderably from the typical mature form ; this difference was specially 

 noticeable in the immature males, which had the cephalosome and 

 first free body segment much shorter than in a full-grown specimen. 

 The difference was so great in this respect, that had one or two 

 mature males not turned up, I should have hesitated to ascribe the 

 specimens to C. equilibra. 



The occurrence of these Crustaceans under the circumstances 

 described is of interest from its bearing on the dispersion of species, 

 and as an example of one of the various means by which forms 



