Wisner and McMillan: Review of new world hagfishes of the genus Myxine 



531 



known species, M. ios from the eastern Atlantic and M. 

 capensis from South Africa are compared briefly with 

 the new world species M. pequenoi. Both M. garmani, 

 and M. paucidens Regan, 1913 are known only from 

 Japan and are not closely related to any new world 

 species. The number of new species (nine) from near 

 the coasts only, suggests a need for further and more 

 intensive collecting throughout the world. 



Methods 



Methods of counting and measuring generally fol- 

 low those of Fernholm and Hubbs (1981) and 

 McMillan and Wisner ( 1984). All measurements are 

 in mm, and body proportions (Table 1) are in percent 

 of total length. Features used in measuring and 

 counting are shown in Figures 1 and 2, and geo- 

 graphic distribution in Figure 3. Counts of slime 

 pores (Tables 2-5) and unicusps (Table 6) represent 

 the left side only because we have found no signifi- 

 cant differences between the left and right sides. 

 Occasionally one extra gill pouch occurs, usually on 

 one side only and much smaller than normal; one 

 less pouch rarely occurs on either side. The one to 

 three slime pores which may occur over the 

 pharyngocutaneous duct are included in the 

 prebranchial pore count. In all species of Myxine only 

 two fused cusps (a multicusp) occur on the posterior 

 set of cusps (inner row of Fernholm and Hubbs, 1981 ) 

 in contrast to either two or three on the anterior set. 

 This latter character is used to group species (Tables 

 1-7). Some terms have appeared previously in 

 myxinid accounts without clear definition. We offer 

 precise definition of these and some new terms used 

 in this study: rostrum, rounded to pointed, fleshy 

 extension lying over the nasal orifice between the 



anteriormost pairs of barbels; head, from tip of ros- 

 trum to a vertical from wrinkled tissue below the 

 mouth; face, ventral aspect of head; mouth, the elon- 

 gate slit in face which opens to permit extrusion of 

 cusps for feeding (Fig. 2A); multicusp, a unit of two 

 or three cusps (teeth of other authors), fused together 

 at bases (Fig. 2B); unicusp, a single unfused cusp 

 (Fig. 2C); pores (slime pores), the small openings 

 along the ventral aspect of body which emit mucus; 

 gill aperture (GA), the opening through which wa- 

 ter discharges to the exterior after passing through 

 the gill pouches; PCD, the external opening of the 

 pharyngocutaneous duct, always on the left side and 

 usually confluent with the left gill aperture in Myxine 

 (or posteriormost GA in Eptatretus); ventral finfold 

 (VFF), a band of thin, fleshy tissue extending along 

 ventral midline of body between PCD and origin of 

 cloaca (Fig. 1); cloaca, the slit-like ventral opening 

 anterior to tail through which body wastes and sexual 

 products discharge; and caudal finfold (CFF), the 

 band of thin fleshy tissue extending around tail, end- 

 ing dorsally about over origin of cloaca (Fig. 1). 



Colors are determined after scraping away the 

 coating of coagulated slime (mucus). Although given 

 in the descriptions, color is subjective and may 

 change greatly with preservation; therefore, the use 

 of counts is preferred as a more distinguishing char- 

 acter. Because eggs are similar in all species, we have 

 not used them as a species character. They vary 

 widely in length and diameter and in developmental 

 stages, ranging from tiny to nearly mature in females 

 of the same length. Accurate measurement of diam- 

 eter is hindered in eggs deformed because of crowd- 

 ing in life or during preservation; many are some- 

 what flattened and diameters may vary as much as 

 1.5 mm in the same specimen. We have not provided 

 photographs or drawings of individual species since 



F G 



Figure 1 



Sketch of a Myxine showing features used in measuring and counting: A-G = total length 

 (TL); A-B = prebranchial length; C = opening of the pharyngocutaneous duct (PCD); D = 

 ventral finfold (VFF), D'= enlarged portion of VFF with dashed line indicating the ap- 

 proximate difference between a well and a weakly developed VFF; E = origin of cloaca; 

 E-G = tail length; F = caudal finfold (CFF). The many slime pores along the sides are 

 indicated by a few small circles near PCD and cloaca. 



