2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 79 



Out of the confusion Cerfontaine rescues the worm first described 

 by Kuhn from ScylUuTn catuhis as Onchocotyle appendiculata, giv- 

 ing it the name Acanthonchocotyle appendiculata. This certainly 

 has nothing to do with the form described by P. J. van Beneden 

 (1858) as O. appeTidiculata from Miistelus vulgaris^ nor with others 

 described under that name. The other known species of the genus 

 is Acanthonchocotyle caniculi Cerfontaine from Scylliuni canicida. 



ACANTHONCHOCOTYLE MUSTELI. new species 



Plate 1, Figure 5 



JSpedflc diagnosis. — Acanthonchocotyle : The present form, a very 

 minute worm from the gills of Mustelus canis, must belong to this 

 genus, but it does not agree with either of the two forms described 

 by Cerfontaine, and we have therefore regarded it as a new species. 

 In general form it agrees precisely with the generic description but 

 differs in detail. 



The body measures 2 mm. to 2.5 mm. in length by 0.5 mm. in 

 breadth. The fixation disk is rather fan-shaped, the appendix start- 

 ing up from its junction with the body. The large suckers are all 

 about the same size. The form of the hooks (fig. 1, c) differs 

 slightly from either of those shown by Cerfontaine (1900) in his 

 Plate 19, Figures 5 and 6. The small booklets are of moderately 

 stout build (fig. 1, c')- The mouth sucker is not so wide as the body, 

 but is thin walled and flares a little. The pharynx is small and com- 

 pact and situated a short way behind it. The intestine is incon- 

 spicuous and does not visibly enter the fixation disk. 



The penis is armed with about 60 minute spines, which take differ- 

 ent positions according to its degree of evagination. The vaginal 

 orifices appear at first sight to be armed with chitinous spines 

 folded together in a bundle, but in one specimen the position is such 

 that one can look into these orifices, and it is then found that there 

 is a radiate chitinous margin with a starlike arrangement of wavy 

 chitinous points about the central orifice. The wide vaginal canals 

 run all the way back to join the vitelline duct (pi. 1, fig. 5). The 

 ovary is much lobulated and situated at about the middle of the 

 body. The uterus is a long straight tube without any coils or defi- 

 nite ootype. Testes form numerous small lobules with a wide, 

 coiled vas deferens. The eggs measure 176/x by 56/a, and while the 

 anterior pole is blunt, there is an extremely long, fine filament at 

 the posterior end that coils far back in the uterus. 



A. musteli is distinguished from other species of this genus by the 

 form of the booklets and hooks and by the chitinous armature of the 

 vaginal orifices. 



Type specimen. — U.S.N.M. Helm. Coll. No. 8131; paratypes 

 No. 8132. 



