HIPPOGLOSSINA YAGRANS. 221 



fifty fathoms or less, thus bringing themselves among the shoal-water forms. 

 This will be made sufficiently clear by examination of the list with least and 

 greatest depths. Glyptocephalus cf/noglonsus is a marked instance, ranging as 

 it does from a depth of less than a hundred fathoms to one of more than 

 eiglit hundred. 



That there was a comparatively recent connection between' the Pacific 

 and the Atlantic across the isthmus, and that separation of the two oceans 

 affected the shoal water forms more recently than the forms of the deep 

 sea is favored by the representatives of the Pleuronectidaj in this collection. 

 Close affinities exist between the species of Citharichthys, Platophrys, Sym- 

 phnrus, and Monolene from opposite sides of the isthmus. These relation- 

 ships are especially noticeable in the species of Symphurus and even more 

 so in those of Monolene, 31. maculipinna and M. sessilicauda, for instance. 

 Type specimens of M. sessilicauda at hand have forty-five vertebrse, as in 

 M. macidipimia, instead of forty-three as was originally stated in the generic 

 diagnosis. 



In the " Challenger " Eeport, published in 1887, Dr. Giinthcr gives a 

 list of nineteen species of Pleuronectoids known to occur at depths greater 

 than one hundred fathoms ; the works of the " Talisman," the " Albatross," 

 and the " Investigator " have since increased the list so that it now contains 

 fifty-five species. 



PLEURONECTID^. 

 Hippoglossina vagrans var. n. 



D. 59-60; A. 44-47; V. 6 ; P. 11 on each side; C. 17; LI. 73-77; Ltr. 

 21-22 + 23-26. 



Body sinistral, compressed, greatest depth near midway from snout to 

 base of caudal about one third of the total length, profile outlines on dorsal 

 and ventral edges curving regularly from the deepest portion forward to the 

 eyes and backward to the caudal pedicel. Head two sevenths of the entire 

 length, with a narrow sharp ridge separating the eyes, with a prominent 

 angle below the symphj'sis of the lower jaws and another below the angular, 

 and with a wide indentation in front of and encroached upon by the upper 

 eye. Snout hardly three fifths as long as the eye, lower jaw longer. 

 Mouth wide ; maxilla with a low prominence anteriorh^, reaching backward 

 of the middle of the left eye. Nostrils small, left pair in front of the inter- 



