ROTATORIA OF THE UNITED STATES. 
337 
Measurements. — Length of body, 0.12 mm.; of toe, 0.13 to 0.14 mm.; total, 0.25 to 0.26 mm. 
History. — This species was described by Pell in 1890 as Mastigocerca bicuspes. Stokes rede- 
scribed it in 1897 as Mastigocerca spinigera. It has been figured by Jennings (1900 and 1901). 
Distribution. — I have found this species as follows: East Harbor, Lake Erie, near Sandusky, 
Ohio; Graveyard Pond, Presque Isle, near Erie, Pa.; Huron River at Ann Arbor, Mich. Pell 
(1890) does not note where he found this species. Stokes (1897) described it from a pool near 
Trenton, N. J. It has not yet been recorded from Europe. 
32. Rattulus elongatus Gosse (pi. xii, figs. 102-107). 
Synonyms: Mastigocerca elongata Gosse (1889); Mastigocerca grandis Stenroos (1898). 
Distinguishing characters. — This species may be known by its large size, its elongated form 
tapering toward the posterior end, the very long main toe accompanied by a •“ substyle” one-sixth 
to one-fourth its length, and the unarmed anterior edge of the lorica. 
External features. — The body is long and slender, somewhat larger at or near the anterior end 
and tapering back to a slender foot. The dorsal line is somewhat arched, the ventral line nearly 
straight (fig. 105). The anterior portion of the lorica, or head-sheatli, is not marked off from the 
remainder of the lorica bv a constriction. The anterior edge is without spines or teeth. 
The dorsal surface of the lorica bears a broad, transversely striated area extending backward 
about one-third the length of the lorica. The anterior part of this striated area (a little less than 
one-half of its length) is depressed, so that there is a rather broad furrow extending from the ante- 
rior edge backward for a distance somewhat greater than the diameter of the body (to the point x, 
figs. 102 and 105). Near the posterior end of this furrow is the opening for the dorsal antenna (fig. 
102, cl. a. ) . That part of the lorica forming the bottom of the furrow projects a little at the anterior 
edge of the lorica (fig. 102). 
When the head is extended it is covered with a somewhat stiffened membrane which lies in 
transverse folds, giving this region a wrinkled appearance (figs. 103 and 104). 
Corona. — The corona seems of the usual character. There is a large club-shaped dorsal 
process (not shown in the figures) , but lateral processes have not been observed with certainty. 
Antennce. — The dorsal antenna is in the dorsal furrow near its posterior end. The lateral 
antennae are in the usual position (figs. 102 and 105) save that the right one lies much farther 
toward the dorsal side than does the left, if the position of the dorsal antenna is taken as indicating 
the dorsal middle line. In a dorsal view only the right one of the lateral antennae shows (figs. 102 
and 103). 
Foot. — The foot is more slender than usual, but is otherwise of the ordinary form. The lorica 
projects farther over it on the left side than on the right, so that the foot may bend to the right, 
but not to the left. 
It will be noticed that there are a number of features in this region which seem to indicate 
that the posterior part of the animal is to be considered as twisted, so that the primitively dorsal side 
is now turned to the left, the primitively right side being dorsal. The attachment of the foot to 
the body is one of these features; usually in rotifers the body projects over the foot on the dorsal 
side, not on the left side. The position of the lateral antenna; indicates the same thing; the left 
one is now far over toward the ventral side, the right one nearly dorsal (fig. 103) . Still more strik- 
ing, from this point of view, is the attachment of the toes to the foot. The two toes are no longer 
side by side, but the primitively right (rudimentary) toe lies almost directly above the left (main) 
toe (fig. 105). If the hinder part of the body could be twisted about 90° to the right all these 
structures would regain their usual positions. 
Toes (fig. 106). — The main toe (Z. t.), representing the left toe of the genus Diurella, is a long, 
nearly straight, tapering rod, two-thirds to four-fifths the length of the lorica. The right toe 
(r. t.) is rudimentary, but is nevertheless much better developed than in many species of the 
genus Rattulus; it is a crooked spine from one-sixth to one-fourth the length of the main toe. 
From its base it curves ventrally toward the main toe, which it crosses (fig. 105). As has been 
set. forth in the account of the foot, the base of this, primitively the right toe. lies in this animal 
almost directly dorsal to the main (left) toe. Both the main toe and the rudimentary toe are 
accompanied at the base by scale-like substyles, each toe having at least two of these (fig. 106). 
F. C. B. 1902—22 
