ORGAN OF THE SILUROID HYPOPHTHALMUS. 



117 



settle definitely the relations of Ilypoplithalmus to that family. It is evident from the 

 researches of Reissuer, that considerable limits exist as to the development of the air- 

 bladder and Weberiau apparatus in the Hypostomes ((/. Rhinelepis and Loricaria). I hope 

 in some future studies on the Siluroids, to call further attention to the remarkable modifi- 

 cations which the skull and anterior vertebrie undergo in the group. 



LIST OF LITERATURE REFERRED TO. 



1. CoiH?.— Proc. Am. Ass. Adv. Sci., 1S71. 



2. Gill— Arrangement of the Families of Fishes : Proc. Smithson. Inst., Vol. XL 



3. Goldi— Jeuaische Zeitschrift, Vol. XVII, 18S4. 



4. Giinther— Brit. Mus. Cat. Fishes, Vol. V. 



5. Reissner— Arch, fur Anat. u Phys., IS.'ii). 



G. Sagemehl — ^lorphologisches Jahrbuch, Vol. X, 1884. 

 7. Solger— Arch. Mikr. Anat., Vol. XVIII. 



S. Weyenbergh — Mémoire Anatomique sur Hijpoiiomusplecoslomw, Cordoba, 1S7G. 



9. Wright, R. Ramsay, McMurrich, etc. — Contributions to the Anatomy of Amiurus, from Proc. Canad. In st. 

 Toronto, 1884. 



10. Wright, R. Ramsay— Jour. Anat. Phys., IS85. 



11. Wriglit, R. Ramsay — Zool. Anzeiger Vol. VII, p. 248. 



12. Jordan and Gilbert — Synopsis of the Fishes of North America. 



DESCRIPTION OF PLATES VIII, IX, and X. 



All the figures are illustrative oî Hypophlludmm viarginatus. 



Fig. 1. — Cranium and anterior vcrtebrtc from above slightly enlarged. 



Fig. 2. — The same from below. 



Fig. 3. — Side view of posterior end of cranium and anterior vertebrse. 



Fig. 4. — Opercular apparatus and jaws from the lateral aspect. 



Fig. 5. — Shoulder-girdle from above. 



Fig. fi-lfi. — Selected sections from a series of over 300, extending from shortly behind the trigeminal foramen to 



behind the foramina of the Gtb spinal nerve. 



Of these Sections, Fig. (i represents the 19th, 7 the 30th, S the 43rd, il the ]2Gth, 10 the 142nd, 11 



the 155th, 12 the lU2nd, 13 the 168th, 14 the 175th, 15 the 187th, Ki the 217th; while the ôth 



spinal nerve escapes in the 257th, and the lith in the 293rd. 



The enlargement is about 8 diam. lin. 



LIST OF LETTERING EMPLOYED IN THE PLATES. 



a atrium sinus imparls. 



aasc ampulla of anterior semicircular canal. 



ab air-bladder, ab' ab-, its membranous and os- 



seous portions. 



an autorbital. 



apse ampulla of pcisterior semicircular canal. 



art articulare. 



a.s alisphenoid. 



aso anterior semicircular canal. 



bo basioccipital. 



bs basisphenoid. 



c' centrum of 1st vertebra. 



ca' cartilage jiersisting between spheuotic and 



pterotic. 



ca'- cartilage persisting between supraoccipital and 



osseous roof of neural canal. 



hmd hyomandibular. 



