^33 ^- Goi'O- 



T. tmchuitiim, was described by Monticelli'>; and finally in 1891 three species 

 were added to the genus, two [T. iiiterrejjtum and T. Levinsenii) by Monticelli-^ and 

 one (r. histiopliori) by Jeffrey BelHX 



The emended generic diagnosis of D i e s i n g*) is as follows : " Corpus suborbicn- 

 lare v. oblongum, planum v. depressum. Caput discretum, acetabulis duobus margin- 

 alibus V. juxtapositis subcircularibus. Os inter acetabula subterminale. Acetabulum 

 corporis radiatum ventrale inferum, sessile, disciforme explanatum, intus septemradi- 

 atum, disco centrali minore. Androgyna; aperturae genitales approximatae, 

 feminea infra os, mascula in sinistro corporis latere, pane filiformi. Porus ex- 



cretorius Tractus intestinalis bicruris, coecus. Ovipara. — Piscium marinorum 



ectoparasita." Following closely Braun and S t .- E e m y I give the generic diag- 

 nosis as follows : 



Body circular to el on gated -oval, much flattened; with 

 two circular or elliptical anterior suckers at the anterior 

 end of the body on either side of the subterminal mouth, 

 and a single circular sessile sucker at the posterior 

 extremity. Posterior sucker provided with a mar- 

 ginal membrane, with its internal surface divided by 



* 



means of a certain number of radial septa and the bars 

 connecting them, into a central polygonal area and 

 a certain number of peripheral areas; generally car- 

 rying hooks (mostly one pair). Uterus opening into 

 the genital atrium or independently of it directly to the 

 exterior. Genital opening or openings, ventral, on the 

 left side of the body near the anterior sucker. With a 

 vagina opening ventrally on the left side of the body, 



1). Monticelli — Tristomum uncinatum, n. sp. Boll. d. Soc. d. Nat. in Xapoli. An. Ill, fasc. 

 II. 1889. pp. 117-119. With one plate. 



2). Monticelli — Di alcuni organi di tatto nei Tristomidi : Contributo al. Stud. d. Trem. 

 monog., parte I. BoU. d. Soc. d. Nat. in Napoli. Ser. I., ann. 5., vol. 5, 1891. p. 122, 

 Notes III & IV. 



3). Jeffrey Bell — Description of a New Species of Tristomum from Histiophorus breviros- 

 tris. Annals & Mag. of Nat. Hist, vol. VII, 6tli. ser., 1891. pp. 534-533. 

 4). Diesing — Revision d. Myzhelminthen, p. 365. 



