1 >r. ('. A. Kt)loi(l on I'li'oiluriiiu illiin)i.si.'ii.sis. \'.V.\ 



fc>kull : basil;\r leiigtii (of a second s])ccimcn) •17'5 ; nasals 

 (of type) 18-3*xi<-5; intcrorbital breadth 20*5; inter- 

 temporal breadth lll"2 ; diastema 17"8 ; length of upper molar 

 series 10*4 . 



JJah. ^louth of Coea lliver, Upj)er Kio Na])o. 



T7/j>e. Male. li.i\I. no. 0. 6. ."i. 4. Collected in June 1899 

 and |)re8ented by Mr. Walter Goodfellow. 



It is probable that just as S. tricolor ranges northwards 

 from Maynas to the Coca lliver, so S. coca/is w[\\ be found to 

 range up that river westwards and northwards, and that the 

 two species only overlap just at this |)oint. As the two 

 species are found together it may be well to emphasize their 

 differences by repeating that JS. cocalis^ as represented by 

 seven specimens, ditlers from S. tricolor (1) by its grizzled 

 instead of blackish crown, (2) by the light patches behind tlie 

 ears, (3) by its bright orange instead of chestnut fore limbs 

 and hind feet, (4) its black-lined sides, (5) its basally ringed 

 caudal hairs, and (G) its shorter muzzled skull. 



Sciurus pyrrhonotuSj Wagn. 



Yungas and Missiones, on the Upper Mamor^, Bolivia 

 (L. Balzan, in Museo Civico, Genoa). 



The type locality of S. pyrrlwi^otus is Borba, near the mouth 

 of the Madeira, so that its occurrence on the Mamord, on the 

 far upj)er waters of that stream, affords another instance of 

 the manlier in which the ranges of these squirrels follow the 

 lines of the great Amazonian rivers. 



XV. — Plankton Studies. — II. On Pleodorina illinoisensis, a 

 ntiv Species /rom the Fluukton of the Illinois River. By 

 C. A. KOFOID, Ph.D.t 



[Plates V. & VI.] 



The genus Pleodorina was discovered in 1893 by Shaw 

 (1894) at Palo Alto, California, and in May of the following 

 year ti.e species Pleodorina cafi/ornica, upon which the genus 

 was toundcd, was detected by Mcjttier (1894) in water from a 

 shallow stagnant pool near Bloomington, Indiana. During 



• Diagonally. 



t From the ' l?ulletin of the Illinois State Laboratory of Natural His- 

 tory,' vol. V. pp. l'7.i l'i'3. From a separate impression comuiunicatcd by 

 the Author. 



