OF THE PEilIDINI3:A. 575 



ential character between Glenodinium and Peridinium, yiz. the existence of a 

 red speck in the former, is worthless ; and were no other peculiarities discover- 

 able, the two genera should be merged into one. However, the elongation of 

 the lorica into horn-like processes supplies a differential character sufficient 

 at least to constitute two genera out of their several members. Ehrenberg re- 

 cognized this inchcation of a division, and adopted it for his eyeless Peridiniaea, 

 making two sections : — 1, Peridinium proper ; and 2, Ceratimn, horned Peri- 

 dinia, Perty, we have seen, uses the same structural peculiarity as a generic 

 character, but, in addition, makes a third genus, marked by the absence of 

 sculpturing on its lorica. This basis we hold to be insufficient for a generic 

 distinction ; and the whole of the Peridiniasa proper appear to us reducible to 

 the two genera Peridinium and Ceratium; Glenodiniion we would conse- 

 quently cancel. The rejection of Ehrenberg's views of internal organization, 

 and of two of the four genera he classed as Peridiniaea, renders a revised 

 description of this family necessary. In attempting this, we may state that 

 the Peridiniaea are animalcules having an external, condensed, chitinous inte- 

 gument forming a lorica, lined by a contractile membrane immediately invest- 

 ing the organic contents. 'No actual oral opening is satisfactorily made out ; 

 but in most species a deep fossa or fissure is found, from the bottom of which 

 a flabehum extends, mostly twice or more than twice the length of the body. 

 Their figure is more or less globular or ovate ; and sometimes the lorica is ex- 

 tended into two or three long horn-like processes, giving the whole being a 

 very bizarre appearance. A deep fiuTow surrounds the body as a zone, and in 

 some species a vertical prolongation of it extends to one pole. These furrows 

 are richly ciliated ; yet the cilia do not appear confined to them, as Ehrenberg 

 supposed, but may, at least in one species, cover the entii^e sm-face. The 

 interior is occupied by masses of usually strongly-coloured brownish yellow, or 

 reddish or greenish brown, rendering the animalcules very opake. In some 

 species an oval nucleus has been seen ; and its presence is presumable in all. 

 A contractile vesicle has not yet been demonstrated. They multiply by 

 transverse, and it may be also by longitudinal fission. P. uberrimum has been 

 found in a quiescent condition ; and doubtless some mode of propagation exists ; 

 Perty endeavours to prove it is by internal germs. The zone-like ciliary 

 furrow may be adduced as the leading characteristic. 



Genus CILETOTYPHLA. — Lorica silicious, hispid or spinous, destitute of 

 a transverse fiuTow or zone, and of stigma ; surface covered with little spines 

 and bristles, which appear stronger at the posterior portion of the body. The 

 lorica may be crushed by pressure, and the httle creatiu-e within it be set at 

 liberty. In swimming it revolves upon the longitudiaal axis, probably by 

 means of a delicate filiform proboscis, or of cilia at its mouth ; no such organs, 

 however, have been seen. Of the internal organization, nothing positive is 

 known. One species has been discovered in flint, and so closely resembles 

 Xanthidium, that it is often mistaken for it. 



CiL^TOTYPHLA cirmcita. — Ellipsoidal, | C. aspera. — Brown, oblong, rounded at 

 browTi, ends rounded ; covered posteri- | both ends, and rough, with short bristles ; 

 orly with short spines, where there is a I the little spines are scattered without 

 circlet of black spots, as sho^na in the i order at the posterior end. Fomid with 

 end view, x. 215. The anterior ciHa, or | the preceding. 1-570". 

 fine bristles, are sometimes very indi- I C. (?) Pyritce. — Oblong cylindrical, 

 stinct ; x. 214 is a variety in which they | rounded at both ends, and provided with 

 are strongly marked. In clear water, j delicate elongated bristles, but no spines, 

 amongst Confervae. 1-620". i Fossil in flint, near Delitzsch. 1-1150". 



Genus CH^TOGLENA. — Lorica silicious, destitute of a transverse zone 



