ART. 21. PARASITES OF SHARKS AND SKATES LINTON. 19 



muscles. It is continuous at the lateral margins, thus surrounding 

 the regions in which the longitudinal vessels and the lateral nerves 

 lie. 



The uterus is median in position, being nearly circular in its out- 

 line in sections of adult proglottides in both transverse and sagittal 

 sections. 



While there would seem to be no reason to doubt that these Alaska 

 specimens belong to van Beneden's species, nevertheless, when one 

 considers the details of the anatomy, given in Zschokke's excellent 

 description of this cestode, differences appear which can not well be 

 ignored. 



1. Zschokke's figure of the scolex ^ shows elongated bothria which, 

 it is hard to see could contract into the shape w^hich all of my speci- 

 mens uniformly have. 



2. The figure of the uterus ^ shows a much more sacculated struc- 

 ture than I find in sections made at relatively the same stage of de- 

 velopment. 



3. In the plan of the reproductive system^*' while my material is 

 far from being all that could be desired, I find a distinct ootype, that 

 is, a muscular, funnel-like beginning of the germ duct; also the 

 oviduct enters the uterus a little above the posterior third, instead 

 of at the anterior end. 



4. Both Beneden and Zschokke speak of ripe proglottides becom- 

 ing longer than broad. In my specimens, even those which have the 

 uterus bulging with eggs, the breadth of the proglottides is more 

 than four times the length. 



5. In my sections I find no trace of the " stiff, slightly recurved 

 bristles " on the neck, nor the " dense covering of villi " of the re- 

 mainder of the body, mentioned by Zschokke. As already stated, the 

 outer layer of the cuticle in longitudinal sections of the Alaska ma- 

 terial appears to be composed of short, blunt papillae, but these are 

 sections of fine transverse corrugations on the surface of the strobile. 



I venture the suggestion that Zschokke's material from Catulus 

 stellaris is specifically different from Beneden's material from Som- 

 niosus brevipiwna {Scymnus glacialis, and Laeinargus 'boreoHis of 

 Beneden's papers are synonyms; see Jordan and Evermann, Fishes 

 of North America (p. 57) ). 



* Recherch. sur la Structure Anatomlque et Histologique des Cestodes, flg. 114. 

 9 Idem, fig. 120. 

 '"Idem, fig. 119. 



