Chydorus faviformis. 
307 
Material collected in 1893 from northern Wisconsin by Mr. L. 
'S. Cheney contains specimens which leave no doubt of the spe- 
•cific identity of this form with P. hastatus. . 
Chydorus faviformis, sp. nov. 
Plate XIII, Figs. 7, 8. 
Female.—The form is in general similar tb that of C. 
sphcericus. The shell of the head and body is covered with deep 
polygonal cells, formed by outfoldings of the outer layer of the 
valves. These give the shell an appearance like a honeycomb, 
whence the specific name. The postabdomen is broad, the end 
rounded and the anal projection large. There are 9-10 post-anal 
teeth. The terminal claws are serrate and bear one basal tooth. 
This species is transparent and yellowish. Length, 0.5-0.0 mm. 
Found in shallow water in the lakes at Minocqua and at Twin 
lakes, Wis., and in G-ogebic lake, Mich. This remarkable spe¬ 
cies was first seen at Minocqua, where cast, shells were found 
and afterwards living specimens in abundance. The main pecu¬ 
liarity of the species is the development of the deep pits on the 
surface of the shell. These are identical with the structures 
occasionally seen in other species of Lynceidse. Leydig (’60 
p. 224) says of Pleuroxus trigonellus : “Als etwas besonderes fiel 
mir noch auf, dass bei der Seitenlage des Thieres (und unter 
starker Yergroesserung) auf der Woelbung des Kopfschildes sich 
ein eigenthuemlicher, zarte'", senkrecht gestellter Hautsaum hin- 
zieht, ungefaehr auf der Mitte des ScheiteJs beginnend und bis in 
der Herzgegend sich erstreckend. “ 
Schoedler (’63, p. 45.), noted the same fact. P. E. Mueller 
{’68, p. 190.), observed the same structure in this species and 
also in P. personatus , in which he figured it (P. IV, f. 23.), and 
showed that it consists of hexagonal cells corresponding to the 
reticulations. Kurz (’74, p. 68.), correctly explained and fig¬ 
ured it in P. trigonellus , (P. Ill, f. 5). Hellich (’77, p. 104.), 
noted it in P. trigonellus. Matile (’90, p. 54.), described the 
occurrence of the “Cuticularsaum” in P. trigonellus , personatus 
and aduncus , and in Chydorus sphoericus. 
