52 Dr. Johnston's Cofitributions to the British Fauna. 



Art. VI. Contributions to the British Fauna. By George 

 Johnston, M.D.^ Fellow of the Royal College of Surgeons 

 of Edinburgh, 8^c. 



[Continued from Vol. III. p. 491.] 



In a preceding communication I had occasion to mention that the 

 Gammarus marinus of Leach was common in this neighbourhood; 

 but from a subsequent examination of my specimens I am now con- 

 vinced that I was in error, and that they constitute a distinct and uncha- 

 racterised species, which I proceed to describe. 



Gammarus carinatus. 



G. corpora maculato, atomisque flavis irrorato; dorsi segmentis valde 

 carinatis, marginibusque posterioribus granulatis. 

 Hub. Mare Britannicum. 



Desc. Body one inch long, inflected at the tail, clouded with red 

 and horn-colour, and sometimes with white, and sprinkled on the sides 

 with minute yellow grains. Segments roughish, punctured, with a row 

 of rather distant granules on their posterior margins ; each with a cunei- 

 form process, which forms, by its junction with the others, a strong and 

 acute keel along the back. The keel commences between the antennae, 

 gradually increases, and then again decreases towards the tail. Antenn(E 

 nearly equal, stained or annulated with red, spinous. Superior Antenncs 

 with the first and second joints nearly equal, third rather shorter, the 

 last with short articulations, each armed with a whorl of very short 

 spines. Seta one-third the length of the last joint, with rather long 

 subclavate articulations. Inferior Antenna: with the basilar joint very 

 short, the second and third nearly equal, and the last similar to the 

 superior. Eyes lunate, brown with a blacker centre, placed at the base 

 of the superior antennae. Hands equal, ahke, obovate, monodactyle. 



