BY T. HARVEY JOHNSTON AND 0. W. TIEGS. 119 



either side of the head. Posterior disc showing a tendency towards sucker-like 

 structure, though no distinct sucker is produced. Correlated with this, there is a 

 diminution or even disappearance of the major hooks. Eyes present or absent. 

 Intestine with or without caeca. Testis single or double. Ovary simple or 

 branched. Cirrus simple. Vagina present or absent. 



Prom the gills of fishes. 



The name C'alceostomidae wa.s first used by Parona and Perugia in 1890, 

 but was employed to designate a subfamily, Monticelli in 1903 raising the sub- 

 family to the status of a family. 



We have subdivided the family into the Calceostominae and Dionchinae. 



Subfamily I. CALCEOSTOMINAE Monticelli, 1892. 

 (Syn. Calceostomidae Parona and Perugia, 1890.) 



Calceostomidae with a bifurcated intestine provided with very marked caeca. 

 Vagina (apparently) present or absent. Testis single. The head develops a pair 

 of head lappets. 



Including the genera Caloeostoma v. Ben., 1858, and Fridericianella Brandes, 

 1894. 



28. Caloeostoma van Beneden, 1858. 



Calceostominae. Large worms, measuring from about 5 to 8 mm. in leng-th. 

 Posterior disc broader than body and somewhat cup-shaped; unarmed or pro- 

 vided with an armature consisting of a central group of two comparatively small 

 hooks as well as minute marginal hooks. From the anterior end, immediately 

 in front of the eyes, are developed a pair of very remarkable head-lappets. A 

 pair of large glands occupy the greater part of the head and open by nmnerous 

 ducts in the vicinity of the mouth. Eyes present (or absent according to ac- 

 counts of the European species). Pharynx large; intestine bifurcated with pro- 

 minent caeca. A single elongated testis; cirrus rather simple. Ovary branched. 

 Vitellaria well developed. Vagina absent. 



Found on the gills of marine fishes. 



Type species, C caloeostoma (Wagener, 1857) J. & T., 1922, Syn., G. 

 elegans van Beneden, 1858. Other known species, C. merme Par. & Per., 1889. 



CALCEOST03IA GLANDtJLOSUM, n.sp. (Plate xsi., flgs. 75-77; xxii., flg-s. 79-86.) 



This is a large worm, measixring about 5 mm. in length and .9 nun. in 

 breadth. 



The disc is broader than the body of the worm and somewhat .cup-shaped in 

 general appearance, with a vei-y strongly crenated margin. The dorsal and more 

 posteriorly lying portion of the "cup" is marked off from the anterior and more 

 ventrally situated part by a prominent septum which has a less strongly crenated 

 free edge (PI. xxii., fig. 86). The anterior section of the cup is rather larger 

 than the posterior and contains the powerful hook apparatus. This consists of 

 two large hooks articulating with a small chitinous complex which, in turn, rests 

 at the end of a long bar of chitin. An intricate system of muscles is developed 

 in connection with the whole apparatus. The hooks are powerful, sharply- 

 pointed and curved almost into a semicircle. The basal part of each is broad, 

 with short irregular projections, the mechanical action of which upon the chitinous 

 complex probably sen-es to give perfection to the action of the whole clasping 

 apparatus. The chitin complex, with which the hooks articulate, rests upon the 

 top of a long supporting bar and is provided on each side, on its more ventral 



