82 Papers from the Marine Biological Laboratory at Tortugas. 



Udonella socialis sp. nov. (Figs. 238-241.) 



This species is near Udonella caligorum Johnston, but is much 

 smaller. 



Body generally linear in outline, cylindrical; in some cases with 

 transverse annulations, thus resembling a leech; anterior end somewhat 

 truncate in contracted specimens. The 2 small, anterior suckers are 

 ovate in outline; pharynx longer than broad. Ovary about middle of 

 body, with large cells; testes, in the larger specimens, smaller than 

 ovary, immediately behind and contiguous with it. The vitelline glands 

 are lateral, subglobular bodies extending laterally throughout the greater 

 part of the length. Near the posterior end of the body, 2 oval structures 

 (fig. 238(7), agreeing in position with the posterior lobes of the vitelline 

 glands, were seen in the larger individuals, which may represent yolk- 

 reservoirs. They do not resemble the tubular organs represented in 

 figures of U . caligorttm. Posterior sucker cup-shape, circular, unarmed. 



Adults, young, and eggs were attached to the two copepods. There 

 were also numerous empty egg-capsules, from which the larvae had 

 escaped, a few with larvae already developed, and a few with the larvae 

 in the act of escaping from the eggs (fig. 241 ^, j, k). 



Host, Argulus sp., in mouth of Neomcenis griseus: 1908, July 4, 

 2 fish. 



Two copepods in mouth of one of the fish; many trematodes and 

 eggs of same attached to the 2 copepods. 



Twenty trematodes were counted on the edges and ventral surface 

 of one of the copepods, and there were others on the dorsal side. Each 

 egg is fastened to its host by means of a filament which is attached to the 

 smaller end. Dimensions, life: Length 0.71; breadth, anterior 0.14, 

 middle 0.27, posterior 0.15; posterior sucker 0.21; ova 0.15 by 0.09. 

 Dimensions of another, compressed: Length 1.82; breadth, anterior 

 0.27, middle 0.50, posterior 0.30; ova 0.21 by o.ii. 



ASPIDOCOTYLEA. 



Aspidogaster ringens Linton. (Figs. 236, 237, 237a.) 



Bull. Bureau of Fisheries, xxiv, pp. 367, 397, figs. 243-249; Proc. U. S. Nat. 

 M., XXXIII, p. 104, figs. 98, 99. 



Only one specimen was found. It agrees closely with this species. 

 There is the entire ventral lip with a median shallow notch, the lobed 

 dorsal lip, and the 42 loculi around the border, with the marginal sense- 

 organs between. The median ventral ridge is not evident in the mounted 

 specimen. The pharynx is pyriform, the larger end directed posteriorly. 

 The single testis is near the posterior end on the right side. The ovary 

 is contiguous with the anterior end of the testis. Both ovary and testis 

 are long-oval, the long axis of each corresponding to the long axis of 

 the body. The vitellaria extend from the posterior end of the disk in 

 two narrow lines on each side of the intestine, diverging slightly ante- 

 riorly and reaching to about the anterior third of the disk. Genital aper- 

 ture on the left side of the neck. 



