98 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
PLCESOMA Herrick. 
98. P. lenticulare Herrick. 
From aquatic plants iu Put-iu Bay Harbor, Lake Erie; also in towings from the open lake. 
The synonymy of this species is much confused and has led to a great deal of discussion; an 
excellent summary of this is given by Hood (’95). In a note in the Zoologischer Anzeiger of 1894 I 
pointed out that the generic name Pla-soma, due to Herrick (’85), has the priority for this genus, and 
this has been generally accepted, except by Scandinavian investigators, who cling to the name Gastro- 
schisa, proposed by a Scandinavian, without regard to the laws of priority. In that note I considered it 
probable that this species is the Euchlanis (?) lynceus of Ehrenberg, and in accordance with that view 
I have used the name P. lynceus in my papers of 1894 and 1896. The note above referred to concludes, 
however: “If it be held that this is not the Euchlanis lynceus of Ehrenberg, then Herrick’s name, 
rioesoma lenticulare, has the priority.” In view of recent studies on the genus by various authors 
this conditional statement must be held to represent the more probable view, so that the name 
P. lenticulare should lie used for this species. 
Weber has recently founded the family PLesemadre for this and related rotifers, placing the family 
among the Loricata. In my previous papers I have followed Wierzejski (’93) in placing this genus in 
close proximity to the genus Notops (as formerly constituted), among the Hydatinadse. This disposi- 
tion of the genus has repeatedly been credited to me (Hood, ’95; Weber, ’98, p. 737). While I believe 
that its relationship is much better expressed in this way than by transferring it to the purely artificial 
group Loricata, I must disclaim having originated this view. 
Lake Erie (Vorce, ’82, as “ remarkable rotifer, undescribed” ; Vorce, ’87, as Gompliog aster areolatus 
Vorce; Kellicott, ’96). Reservoir near Hebron, Ohio (Herrick, ’85). Lake St. Clair; Crooked Lake, 
Newaygo County, Mich.; Chippewa Lake, Mecosta County, Mich. (Jennings, ’94, as P. lynceus Ehr.). 
Lake Michigan, Round Lake, Pine Lake, West Twin Lake, and Susan Lake, all in north Michigan 
(Jennings, ’96, as P. lynceus Ehr.). Waters connected with the Illinois River at Havana, 111. (Hem- 
pel, ’93, under name P. lynceus Ehr.). 
P. hudsoni Imhof. — Lake St. Clair (Jennings, ’94). Lake Michigan and Round Lake, near Charle- 
voix, Mich. (Jennings, ’96). 
P. truncatum Levander. — Among the specimens of P. lenticulare found in Lake St. Clair in 1893 were 
numbers of a smaller form, with a more wrinkled, less angular lorica. Notes were made at the time, 
but thinking it might possibly be a young form of P. lenticulare, I did not describe it. It has since 
been described as a new species, P. truncatum, by Levander; this must, then, be added to the list of 
species inhabiting Lake St. Clair. It has since been found by Kellicott (’97) in Sandusky Bay, Lake Erie. 
P. molle Kellicott. — Sandusky Bay, Lake Erie (Kellicott, ’97). 
Family 21. GASTROPODIDiE. 
GASTROPUS Imhof (’88). 
Weber (’98) has revived this name for the animal which has been called Hudsonella picta and 
Notops pygmceus. The name Gastropus , published in 1888, undoubtedly has the priority as a name for 
this distinct genus unless it be held that Imhof’s description is insufficient for a recognition of the 
animal described. The description is undoubtedly meager, and most investigators have since been 
inclined to disregard the name as insufficiently founded; on that account I also have in previous 
papers used another name. But one investigator in good standing is in a position to force others to 
use a name which unquestionably has priority, when he maintains that he is able to recognize the 
species, one positive instance being worth more than many negative ones. Weber (’98) takes this 
position in regard to Gastropus, so that I believe it best to accept the name which he uses as 
inevitable, without further ado. Moreover, in my opinion, Imhof’s Gastropus stylifer is, as a matter 
of fact, plainly recognizable, and I used this name for the animal iu question as far back as in my 
paper of ’946, dropping it only when opinion seemed unanimous against this view. To the same 
genus are to be referred Notops liyptopus Ehr., Notops minor Rousselet, Notops fennicus Stenroos, and 
Hypopus ritenbenkii Bergendal. 
99. G. stylifer Imhof (’88). (Notops pygmwus Caiman ; Hudsonella picta Zacharias. ) 
A single specimen in towings from Put-in Bay Harbor, Lake Erie. 
Lake St. Clair and Whitmore Lake, Washtenaw County, Mich. (Jennings, '94, under the name 
Notops pygmwus Caiman). Round Lake, Pine Lake, Lake Michigan, and West Twin Lake, near 
Charlevoix, Mich. (Jennings, ’96, as Notops pygmams Caiman). 
G. minor Rousselet. — Sandusky Bay, Lake Erie (Kellicott, ’97, as Notops minor). 
