GENUS ASSULINA— ASSULINA SEMINULUM. 225 



ASSULINA SEMINULUM. 



Plate XXXVII, figs. 15-27. 



Difflugia Seminulum. Ehrenberg: Monatsb. AU. Wis. 1848, 379.* Mikrogeologie, 1854, Taf. xxxv, B, A. 



ii, Fig. 1.— Pritchard : Hist. Infus. 1861, 553. 

 liuglyplia s. Assulina Seminulum. Ehrenberg: Alili. Alt. Wis. 1871, 24(i. 

 Difflugia Semen. Ehrenberg: Abb. Ak. Wis. 1871, 257, 264. 

 Euglypha brimnea. Leidy: Pr. Ac. Nat. Sc. 1874, 226; 1876, 55; 1877, 321. 

 Euglypha tiiieta. Archer: Proc. Dublin Micr. Club, 1875, iu Quart. Jour. Mic. Sc. 1876, 107; Ibidem, 



1877, 103, 330 ; 1878, 105. 

 Euglypha seminulum. Leidy: Pr. Ac. Nat. 8c. 1878, 172. 



Shell nearly as broad as long, compressed oval, brown in color; 

 borders obtuse, spineless; plates hexagonal or oval; mouth transversely 

 oval, with the margin lacerated or irregularly notched 



Size — From 0.044 mm. long by 0.36 mm. broad and 0.016 mm. thick 

 to 0.08 mm. long by 0.072 mm broad and 0.032 mm. thick. 



Locality. — Common in sphagnous swamps. 



In AsstaDina seniiinuluiii the shell is compressed spheroidal or oval, 

 with the breadth nearly equal to the length, and the thickness about half, or 

 less than half the breadth. The dome and lateral borders are rounded or at 

 most sub-acute. The mouth is transversely oval, and abruptly truncates 

 the pole of the shell, or the latter may be slightly prolonged so as to form 

 a short neck. The shell is chocolate-brown in color, of variable shade, 

 sometimes quite light, and in very young individuals colorless, in old ones 

 sometimes very dark At the mouth it usually presents a lighter band of 

 color. See figs. 15-27, pi. XXXVII. 



The shell is composed of minute oval or hexagonal plates arranged in 

 alternating longitudinal series or obliquely parallel spiral rows. The oral 

 plates, lighter colored and thinner than the others, end in irregular processes, 

 which give to the border of the month a lacerated appearance. 



The soft part of Assulina seminulum has the same constitution as in the 

 species of Euglypha. Usually, I have found it to occupy but little more 

 than half the capacity of the shell, as seen in figs. 18, 19. The animal 

 seems to be exceedingly shy or sensitive, and usually after disturbance 

 remains quiescent for a very long time. The pseudopods are few and 

 extremely delicate. 



*Tbe original description of Difflugia Seminulum, by Ehrenberg, in the 'Monatsberichte,' is as 

 follows: "Lorica brevius ovata, fusca, superficie anguste et subtiliter areolata simplici, ostiolo lato, 

 ne denticulf 

 15 EHIZ 



