88 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxm. 



Order ACANTHOCEPH ALA. 



Repre.sentativt's of this order were found in 11 of tiie 51 species of 

 fish examined. They belonged to a single species and were immature 

 and encysted on tlie viscera in all cases, except the rock fish, where 

 they were also found mature in the alimentary canal. These worms 

 have been referred to the new species EcJiinorliynclius medius. 



ECHINORHYNCHUS MEDIUS, new species. 

 Plate IV, figs. 21-30. 



Type.— Cd.i. No. 5796, U. S. N. M. 



Body elongated, nearly linear, diameter greatest just behind l)ase of 

 sheath, whence it tapers gently to the neck; anterior end of body 

 slightly deflected in same direction as the proboscis, which is inclined 

 at an angle of 45"^, more or less, to the axis of the body; anterior end 

 of body also armed wnth sagittate spines, which, on the concave side, 

 extend back a distance approximatel}^ one-third the length of the 

 sheath, and about halt as far on the convex side. The neck is smooth 

 and conical, its length being somewhat less than its diameter at base. 

 The proboscis varies from nearly linear to fusiform, with about 22 

 vertical rows of hooks, and about 20 hooks in one vertical row; hooks 

 strongly recurved, stoutish, of nearly uniform size and shape, except 

 at the base, where for about five rows the hooks are smaller than 

 they are on the remainder of the proboscis. The hooks are deeply 

 immersed in the cuticle and have strong but somewhat narrow basal 

 supports; those near the base are about 0.045 nun. in length, others 

 0.06 mm., spines on l)ody from 0.03 to 0.045 nnn. in length. Sheath 

 rather slender-fusiform, usually more than twice the length of the 

 proboscis. Lemnisci long and slender. 



In the male the testes are two, small, oblong-elliptical, situated about 

 the anterior third of the length and separated from each other by a 

 distance equal to five or more times the length of one. Remainder of 

 male genitalia simple, consisting of the vas deferens and a long-oval 

 cement gland neai- the posterior end; bursa laige, oblong, its length 

 not much exceeding its diameter in mounted specimens which are 

 somewhat compressed. 



The posterior end of the female is rather al»ruptl3' narrowed to a 

 blunt point which is deflected, in some cases almost at right angles to 

 the axis of the body. 



Dimensions, in millimeters, of a nmie mounted in l)alsam: Length, 

 42; diameter, anterior 0.75, at posterior end of sheath 1.35, middle of 

 body 1; bursa, length 1.5, diameter 1.2; neck, length 0.45, diameter 

 at anterior end 0.37, at base 0.57; proboscis, length 1.4, diameter near 

 base 0.45, near tip 0.30; sheath, length 3, anterior diameter 0.3, mid- 

 dle 0.67, posterior 0.3; distance from base of neck to first testis 12; 



