540 MR. J. T. CUNNINGHAM ON THE [ JuDC 1 7, 



7. On Secondary Sexual Characters in the Genus Arno- 

 glossus. By J. T. Cunningham, M.A., F.R.S.E., Natu- 

 ralist to the Marine Biological Association. 



[Eeceived June 10, 1890.] 

 I. Aenoglossits latekna, Giinther. 



The history of the species Arnoglossus lopliotes, Giinther, has heen 

 quite recently reviewed by Dr. A. Giinther in the Proceedings of this 

 Society^ I need not therefore repeat it hero in detaih But it ia 

 necessary to mention that Couch in his ' History of British Fishes ' 

 (1864) recorded that he had examined a dried skin of the form in 

 question at the house of Lieutenant Spence, R.N., at Plymouth, 

 this specimen having been taken, we are told, in the neighbourhood 

 of that port. The only entire specimens examined by Dr. Giinther 

 were one trawled by Prof. Moseley in 1882 near Lundy Island, and 

 one sent from Palermo. 



Until December 1889 I had never met with any specimens in the 

 course of my observations at Plymouth which exhibited the cha- 

 racters ascribed to A. lojiJiotes. At the beginning of that mouth I 

 collected specimens of A. laterna in order to make an attentive ex- 

 amination of its characters. I asked a man employed on the fish- 

 quay to bring me a number of full-grown specimens of the ' Scald- 

 fish,' as the species is called at Plymouth, from the trawling-smacks 

 which came in from the fishing-grounds. Among the specimens he 

 brought me I was much surprised as well as pleased to find a number 

 which presented the peculiarities of A. lopliotes. In fact, whenever 

 the man brought a number of Scald-fish from the trawl refuse, there 

 were more A. lopliotes than A. laterna among them. The specimens 

 were obtained at all parts of the trawling-grounds off" Plymouth, that 

 is from 3 to 15 or 20 miles off the south coast of Devon and East 

 Cornwall. On subsequent excursions in trawlers, both in the neigh- 

 bourhood of Plymouth, off Mounts Bay, and in the Bristol Channel, I 

 found ihat the lopliotes form always occurred along with A. laterna 

 and was more abundant than the latter. 



I of course made a careful examination of the specimens obtained, 

 and was for some time puzzled by the close similarity between 

 the two forms in the majority of their characters. I found, too, 

 on examining smaller and therefore younger specimens that none 

 of them exhibited the elongation of the anterior dorsal fin-rays 

 •which characterizes A. lopliotes, but that this character was confined 

 to specimens above a certain size. I began to think that if the two 

 forms were really distinct species, they were more exactly similar in 

 the majority of their characters than two distinct species usually 

 are. Then it occurred to me to ascertain the sex of every specimen ; 

 and I found that specimens of^. lop>liotes were invariably males, and 

 adult specimens of A. laterna invariably females. Having found 



' "A Cuntribution to our Knowledge of British PleuronectidK," P. Z. S. 

 1890, p. 4U. 



