400 PROCEEDINGS OF THE AMERICAN ACADEMY 



pf) they are longer than at the narrower end of the body, and at both 

 points they have a pretty uniform length, moderate extension, and are 

 very delicate, so as not to be easily observed when the body is in mo- 

 tion. At the anterior transverse furrow they appear to be a little 

 longer than elsewhere, and acting more or less in concert, they have 

 the semblance of a wreath disposed along the edge of the low skullcap- 

 like covering {pc) of the anterior end. 



The cuirass {pc). It is pretty evident that, in the species before us, 

 this is a mere dermal specialization, without any trace of indurated mat- 

 ter which would entitle it to the name of a genuine cuirass. Where 

 vibratile cilia are present no such covering can be said to exist, and as 

 the broad anterior end (A) of the body is devoid of them, its skullcap 

 covering is the only portion of the derm where one could expect to 

 find a cuirass. But this it is only in form, since it participates with 

 the rest of the body in the general expansion when an individual is 

 dying. It has, without doubt, a different character from the rest of 

 the skin, for the style of ornamentation is not of the same kind, and, 

 curiously enougli too, it is less truly ornamented than in the other re- 

 gions of the body, amounting to a mere scattered punctuation ; whereas 

 over the field where the cilia prevail, these punctuations, which are in 

 reality minute, cylindrical, strongly refracting bodies, standing perpen- 

 dicular to the surface of the derm, are arranged in perfectly regular 

 rows, which have a diiferent character in the three regions posterior to 

 the pseudo-cuirass. In the space (Hg. 5, D) between the anterior («/") 

 and posterior (pf) transveise fui-rows, the rows trend longitudinally 

 and transversely ; in the posterior transverse furrow (pf) they have 

 the same arrangement as the last, but they are more closely set to- 

 gether ; and in the region behind the latter furrow they trend in decus- 

 sating lines (P), like those in the carapace of Arcella vulgaris. 



Tills region is also characterized by being divided longitudinally, on 

 the ventral side, by a furrow (fig, 1, 2, G, tnf) which trends in a direct 

 line from the end of the body to the mouth, and gradually widens an- 

 teriorly where it joins the annular, transverse furrow (pf). At this 

 point of juncture the flagellar appendage arises, and opposite to it the 

 anterior edge of the transverse furrow just mentioned forms an inequi- 

 lateral angle at the broader margin (m^) of the mouth, so that the right 

 and left halves of this furrow are rendered asymmetrical ; a character 

 in perfect accordance with that of many, if not of all the Peridiniae. 



2^he nucleus (n) at the period when these observations were made, 



