NO. 2062. NEW ROTATORIA FROM PANAMA— EARRING. 545 



the ventral plate may be said to be joined directly to the dor&al; it 

 has prominent longitudinal ridges. The posterior segment of the 

 body is very large and unusually prominent; it may be considered as 

 beginning near the middle of the ventral plate and is, seen from the 

 ventral side, ovate, broadest posteriorly. Coxal plates are not pres- 

 ent. The first foot joint is extremely long, tapering posteriorly to 

 half its anterior width; the elongate second joint is parallel-sided and 

 strictly terminal. The toes are very long, slender, and slightly 

 recurved in the posterior third. The claw is nearly half as long as 

 the toe, strongly outcurved and slightly recurved; at the base of the 

 claw there is a conspicuous, laterally directed spine. 



Total length, 170 pt; length of body, 108 /(, width, 45 /r, toe without 

 claw, 36 fi, claw, 15 fi; depth of body, 48 /a. 



Type.—Csit. No. 16581, U.S.N.M., from Rio Grande Reservoir (5); 

 but few specimens were collected. 



MONOSTYLA CORNUTA (MUller). 

 Monostyla robusta Murray, Journ. Royal Micr. Soc, 1913, p. 557, pi. 23, fig. 21. 



Murray considere this species different from Trichoda cornuta 

 Muller, as it has a shorter toe and a nearly straight anterior margin. 

 It is quite true that the toe is a trifle shorter than in Miiller's figure, 

 but the specimens studied by Mr. Murray were not fully contracted, 

 and so did not show the lunate anterior margin, which is normally as 

 deep as in Monostyla lunaris. There can be no doubt about the iden- 

 tity of this form and the one figured by Ehrenberg as Monostyla cor- 

 nuta. That Ehrenberg's identification was incorrect is quite possible; 

 as there is no positive proof that he was in error, he is entitled to the 

 benefit of the doubt. M. cornuta has been repeatedly ruled out 

 because MiiUer figures the claw as double; as a matter of fact, a 

 careful examination of large amounts of material of both species 

 demonstrates that the claw is really double in both species, although 

 the two parts are very rarely separated in M. lunaris and seldom in 

 M. cornuta. 



In the Isthmian material two forms of this species occur; one which 

 may be called the normal measures: Length of body 126 /t, of toe 42 

 fx, of claw 9 IX, and a diminutive form with a relatively much longer 

 claw, which measures: Length of body 85 ji, of toe 23 /«, of claw 9 [x. 



The normal form occurs: In a pool near the railroad, between 

 Black Swamp and Gatun (2), few; creek flowing into Camacho Res- 

 ervoir (3), abundant; stagnant pool at EmjDire (4), common; Rio 

 Grande Reservoir (5), abundant; Rio Grande (6), few; pond east of 

 canal at Empire (8), few; Rio Trinidad, about 1 mile from mouth 

 (9), common; above Agua Clara (10), common; at Escoval (11), a 

 single specimen. The long-clawed form was found in Rio Grande 

 Reservoir (5), common. 



34843°— PiocN.M. vol.47— 14 35 



