256 ]^^^. W. Nicoll on the 



In addition to tlie above-mentioned species I have found 

 species of Spelotrema in Alca torda, Oidemia fasca, and 

 Oidemia nigra, bnt their identity is doubtful. From Alca 

 only one immature example was taken; it apparently agrees 

 most closely with Sp. simile. Its length is '53 mm., 

 maximum breadth '29 mm. ; outline club-like; oral sucker 

 •053 mm., ventral sucker '050 x '056 mm.; undivided in- 

 testine *22 mm., diverticula '17 mm., reaching centre of 

 ventral sucker ; genital body on level of posterior half of 

 sucker, not very large. Ovary on same level as sucker, 

 pear-shaped ; testes transversely oval ; yolk-glands almost 

 clear of the testes, lobed but not well developed. 



The species from the scoters is in all probability Sp. 

 pygmceum, which Jameson * has already found in Britain in 

 the black scoter. I found it iu great numbers throughout 

 the intestine of Oidemia fusca, not so numerously in O. 

 nigra. The specimens were unfortunately destroyed before 

 they were thoroughly examined, but from notes made at the 

 time of collection some idea of their nature is to be gained. 

 Length up to "50 mm., breadth '24 mm. ; oral sucker 

 •044 ram., ventral sucker slightly less ; pharynx '025 x '022 

 mm. ; ova •023--025 x -014 mm. These figures agree more 

 nearly with Sp. pygmceum than with Sp. clavifurme, M'hich 

 can be the only two species in question. 



Genus Tocotrema, Looss. 



Three species have alieady been ascribed to this genus, 

 viz., T.lmgua (Crepl.), T.concavum (Crepl.),and T. Muehlingi 

 (Jagersk.) {=Dist. lingua, Crepl., Miihling). They do not, 

 however, appear to form a very homogeneous group. Toco- 

 trema livgua and T. concavum, though agreeing in the 

 possession of a genital sucker which includes the degenerate 

 ventral sucker, differ in several important features, which 

 appear to demand a generic separation. Although it is true 

 that both possess a genital sucker, the structure of this 

 organ is not at all similar in both. The peculiar '' kegel- 

 formiges Korper '' described by Jiigerskiold f in the sucker 

 of Tocoirema lingua is not even liinted at by Miihling % in 

 his description of Distomum concavum. It may be concluded 

 that such a structure is not present in the latter species, for 

 its presence could not fail to have been noted by Miihling. 

 My specimens of an almost identical form show no appear- 

 ance on external examination of such a body, but as I 



* Proc. Zool. Soc. 1902, i. p. 158. 



t Bergens Mus. Aarbog, 1898, ii. p. 10. 



X Arch. 1'. Njiturg. Ixiv. pp. 80-83. 



