CHAPTER V. 



SUB-CLASS MARSIPOBRANCHII 

 (CYCLOSTOMATA).* 



Vermiform fishes with smooth scaleless skin, cartilaginous 

 skeleton and persistent notochord ; with suctorial mouth, single 

 nasal organ, and straight intestine ; without jaws, paired appen- 

 dages, generative ducts, sympathetic system, and conus arteriosus. 

 The unpaired fins are without actinotrichia {dermal fin-rays). 



The Marsipohranchii are vermiform in appearance, varying in 

 length from two feet or more (Bdellostoma) to a few inches 

 {Petromyzon fiuviatilis). The skin is smooth and without scales, 

 and the skeleton is cartilaginous and notochordal. They are 

 without paired fins, but possess an unpaired caudal fin [Myxi- 

 nidae. Fig. 62), to which may be added a dorsal unpaired fin 

 in the posterior region {Petromyzontidae, Fig. 48). In the 



* J. Miiller, Verglcichende Anatomic der Myxinoiden, Berlin, 1835-4.'5. 

 A. Giinther, Catalogue of the fishes in the British Museum, London, 1870. 

 C. Kupffer, Die Entwickelung der Petromyzon planeri, Arch. f. m,ic. Anat., 

 35, 1890. P. Fiii'b ringer, Unters z. vergl. Anat. d. Muskulatur. d. 

 Kopfskelets d. Cyclostomen, Jena. Zeitsch, 9, 1875. W. K. Parker, 

 Skeleton of Petromyzon and Myxine, Phil. Trans., 1883, p. 373. P. 

 Langerhans, Unters. iib. Petromyzon planeri, Ber. d. naturf. Gesellsch. 

 zu Freiburg, 1873. A Schneider, Beitrdge, z. vergl. Anat. etc. d. Wirbel- 

 thiere, Berlin, 1879. T. H. Huxley " On the Cranio-facial apparatus 

 of Petromyzon." Journal of Anat. and Physiology, 10, 1876, pp. 412-28. 

 r. Ahlborn, Das Gehirn v. Petromyzonten. Z. f. w. Z., 39, 1S83, 

 pp. 191-295, and Hirnnerven v. Petromyzon Z. f. w. Z., 40, 1884, pp. 

 286-308. G. C. Price, Ontogenie d. Myxinoiden Bdellostoma stouti, Sitz. her. 

 Math.-phys. Idasse d. k. hayer. Akadl d. Wiss, 26, 1896, Mimich. Id. 

 Development of excretory organs of Bdellostoma stouti, Zool. Jahrbiwh. 

 Anat., 10, 1897, p. 207. ^V. F. R. Weldon, The head-kidney of Bdellos- 

 toma, Q. J. M. S., 24, 1884, p. 171-182. J. W. Spengel, Die Excretions- 

 organe von Myxine, Anat. Anz., 13, 1897, p. 49-60. F. C. Studnicka, 

 Sur le.s organes parietaux de Petromyzon vlaneri, Vestnik Ceske Spol. Natik 

 Prag, p. 1-50, 1893. J. D. Ogilbv, "A Monograph of the Australian 

 Maraipobranchii," Proc. Lin. Sor. N. S. W., 21, 1896, p. 388-426. 



