56 



chronological list of the names under which this rotifer has been des- 

 cribed or mentioned is as follows. 



Euchlanis lynceus, Ehrbg., 1838. 



»Undescribed Rotifer«, Vorce, 1882 (Proc. Am. Soc. Micr., 1882) 



Ploesoma lenticidare, Herrick, 1885. (Bui. Scient. Lab. Denison 

 University, Vol. I, No. I.) 



GoinpJwgaster areolatus,Yorce, 1887. (Proc. Am. Soc.Micr., 1 787.) 



Gastropus Ehrenhergii, Imhof, 1888. (Zool. Anz., Bd. 11, p. 166.) 



Gastroschiza hjnceus (Ehrbg.), Bergendal, Sept. 17, 1892. (Lunds 

 Universitets Arsskrift, Tom 28.) 



Gastroschiza foveolata, Jägerskiöld , Oct. 13, 1892. (Zool. Anz., 

 Bd. 15, p. 447.) 



Bipalpiis lynceus (Ehrbg.), Wierzejski and Zacharias, Nov. 25, 1892. 

 (Zeitschr. f. wiss. Zool., Bd. 56, p. 236.) 



To these is to be added the generic name Dictyoderma , Lauter- 

 born (Sp en g el's Zool. Jahrb., Bd. 7), recently given to another spe- 

 cies of the same genus. 



From the above it appears that the generic name Ploesoma of 

 Herrick, has the priority. If it be held, with Wierzejski and 

 Zacharias, what I believe to be true, that this is the Euchlanis lyn- 

 ceus of Ehrenberg, we have the following synonymy for the species 

 of this genus. 



Ploesoma^ Herrick. 



1) P. lynceus^ Ehrbg. 



Syn. — Ploesoma lenticulare^ Herrick; Gomphogaster areolatus, 

 Vorce; Gastropus Elirenhergii, Imhof; Gastroschiza lynceus ^V>qx^&xi.Òl?i\\ 

 Gastroschiza fov colata , .Jägerskiöld; Bipalpus lynceus^ Wierzejski and 

 Zacharias. 



If it be held that this is not the Euchlanis lynceus of Ehrenberg, 

 then Herrick' s name Ploesoma lenticular e has the priority, and the 

 names Gastropus El irenh er gii ^ Imh., and Gastroschiza lynceus^ Bergen- 

 dal, should perhaps be stricken from the list of synonyms of this species. 



2) P. triacanthum, Bergendal. 



3) P. Hudsoni, Imhof. 



Syn. — Gastroschiza ßexilis y Jägerskiöld; Bipalpus vesiculosus, 

 Wierz. and Zach.; Dictyoderma hypopus^ Lauterborn. 



This species is also found in Lake St. Clair, though it is rare. 



The fourth supposed species of this genus, Gastropus stylif er ^ Imh., 

 Hudsonella pietà ^ Zach., Notops pygmaeus^ Caiman, is very abundant 

 in Lake St. Clair. It has of course been pointed out that this is not 

 a member of the genus under consideration. 



University of Michigan, Morphological Laboratory. Dec. 16, 1893. 



