new and little-knoicn Trematodes. 517 



Dujarclin *, Diosinp:, ]^Ioliii f, Von Linstow \, Cobbold § and 

 Miiller ||, so that its specific cliaiactors are well known. 

 The features which distinguish it from E. secundum arc: 

 (1) the shape of the head, (2) the number of cephalic spines 

 being only twenty-two, (3) the forward position of the testes, 

 (4) tlie curtailed extent of the vitelline f^hinds, (5) the relative 

 sizes of the suckers. That these features are of diagnostic 

 importance in the determination of species is recognized by 

 most observers. According to Muller ^, " several forms 

 appear to be described under E. spinuJosum, which, on more 

 exact knowledge of the number of cephalic spines, extent of 

 vitelline glands, and size of ova, will be distinguished from 

 each other/^ Looss ** discusses the affinities of several 

 species of Echi'nostomum, each possessing twenty-two cephalic 

 sj)ines. They differ from each other in very slight detail, 

 such as the size of the suckers and oesophageal bulb, the 

 size and arrangement of the cephalic spines, and the sizes 

 and positions of the ova, testes, and vitelline glands. 

 It is possible, therefore, that E. secundum may have been 

 already observed and, on cursory examination, mistaken for 

 E. sjjinulusum. 



In the number and arrangement of the cephalic spines 

 Echinostomum secundum probably stands nearest E. lepto- 

 sotnuni, Creplin, described by Villot "ff trom Tringa variabilis 

 {alpina^ and Calidris arenaria. This species possesses 28— 30 

 cephalic spines of length "04 mm. Two spines at each end 

 are on a different level from the others, but according to 

 Villot they do not differ from them in size. The head is not 

 marked off from the rest of the body by a constriction. The 

 suckers also differ in size, while the ventral sucker is distin- 

 guished by the possession of a crenated margin. The oesopha- 

 geal bulb, testes, and ova are all much smaller, altlioiigh the 

 animal itself is nearly iialf as long again as E. secundum. 



Villot describes as the larval form of E. leplosomum, 

 Cercaria leptosoniaj occurring in cysts in the foot of Scrobicu- 

 laria tenuis. Tiiere is much reason to believe that the corre- 

 sponding larval form of E. secundum is identical with that 



• Hist. d. Helm. p. 430. 



t Wit'U. Denkschr. xix. p. 220. 



♦ Arch. f. Naturg. 1877, p. 18:3. 

 § Trans. Liiiu. Soc. xxii. 



II Arch. f. Naturg. Ixiii. p. 20 (1897). 

 ^ Loc. cit. 



** Zoi>l. Jahrbiicher, 1899, xii. p. 689. 

 tt Anu. d. Sc. iiat. Ic79, viii. p. 24. 



