OCULAR AND GKMTAI. H.ATF.S. 



115 



when only 100 were counted. Of course the rarer variants arc usually found in only large 

 series, and one cannot know whether they are rare or not without having examined large num- 

 bers. A series of 229 specimens of Arbaria punctulata from Florida is interesting for compari- 



II 



TEXT-FIGS. 111-114. Ocular plate arrangement in Arbacia imiiriuliita (Ijimarck). \\<H|S llnli-. M u*uu-liuwlln. 

 All figures X 3 (p. 175). 



111. Diam. 31 mm. R. T. J. Coll., 681. M OOUhn OCMrt, typiml character. 



112. Diam. 42mm. R. T. J. Coll., 082. Ocular V insert. 



113. Diam. 31mm. R. T. J. Coll., 683. Oculars V, I insert. 



114. Diam. 38 mm. R. T. J. Coll., 684. Oculars V, I, IV insert . Figure* 1 12 to 1 14 arr all proRmmvc variant*. 



son with those from the northern locality. In the Florida series, 76% have all oculars 

 19% have V alone insert, 2% have V, I and 1% have V, I, IV insert ; :i'',', have an alx-rnmt 

 arrangement, one specimen having ocular IV only insert, and five having V. IV in-ert. In 

 comparing this with the northern form, best seen by the table (p. 158), it is obvious that tin- 

 Florida form is markedly more progressive in ocular arrangement than the northern. 

 in this respect it makes a closer approach to the character of the species occurring off the \ve-t 

 coast of South America. A similar difference seen in the character of a species from different 

 localities is shown also in several other species covering the commoner families of regular Kchini. 



Of the rare species Arbacia dufresnii, 67 specimens are listed in the table. Son ..... thers 

 studied were omitted as too immature for the present consideration. The specimens are largely 

 from San Antonio, East Patagonia, in the de Loriol collection at Geneva. In s7 ' , all oculars 

 are exsert as the species character. As progressive variants, in 4 % ocular V is insert . and in I ' , 

 oculars V, I are insert. Aberrant variants are quite frequent, 7%, as in other South American 

 species of the genus. Of these aberrants, two have ocular IV alone insert, and three have- 

 oculars V, IV insert, I, II, III exsert. This last is a relatively frequent alx-rrant variation in 

 this genus. Eighteen specimens in the de Loriol collection which are considered too immature 

 for tabulation have all the oculars broadly exsert. Of the specimens studied, most have tin- 

 four periproctal plates characteristic of the genus; but two have Mini- periproctal plates, font 

 have five, two have six, and one has nine periproctal plates (compare text-tig>. -JiN) 2<). r >, p. 17:. 



Of the South American Arbacia spatuligera (76 specimens) in only '.' , an- tin- ocular- all 



