12 McMURRICH 



that there can be no doubt, I think, as to the identity of the 

 two forms/ 



I have not in the above discussion considered the variabihty 

 in the number of the siphonoglyphes and directives, which is so 

 pronounced in the European and American East Coast forms, 

 and which might be regarded as of sufficient importance to be 

 regarded as a specific characteristic. Sufficient data are not 

 available to determine definitely whether this variability also 

 occurs in the American West Coast forms, but in the six speci- 

 mens I examined it was not observed. But even granting that 

 no variability in this respect occurs in \\\^ fimbriatmn forms, it 

 does not seem that this would be sufficient for considering 

 these specifically distinct from the marginatum and diantJms 

 forms. No one has suggested that the dianthiis forms with 

 the siphonoglyphe and one pair of directives should be sepa- 

 rated from those with two siphonoglyphes and two pairs of 

 directives, and it would be even less reasonable, it seems to me, 

 to separate fimbriatitm forms from marginatum or diantJius 

 forms with two siphonoglyphes and two pairs of directives, 

 other structural characteristics being so similar. 



There are not at present sufficient data at hand for deter- 

 mining accurately the relative frequency of the monoglyphic 

 condition in the European and fimbriatum forms. To judge, 

 however, from the statements of Thorell ('58), Gosse ('60), and 

 Carlgren ('93), among others, the monoglyphic condition is by 

 far the most frequent in the European specimens ; the thor- 

 ough observations of Parker ('97) show th^t it occurs in some- 

 what over one-half of the total number of marginatum forms 

 which he examined ; while, as stated above, it would seem to 

 be much less frequent in i\i& fimbriattim forms. 



At the close of the list of synonyms of the species I have 



^ To judge from certain statements made by Gosse ('60) I should imagine that 

 the relations of the different color varieties described above for M. inargitiatiivi do 

 not hold for M. dianthits. What the physiological causes may be which produce 

 the different varieties is at present unknown, but a fact quoted by Gosse is of interest 

 in this connection. It is to the effect that on a water-logged board brought in by a 

 trawler there were between four and five hundred specimens of J/, dianthiis, and 

 all the individuals ^'- on one side the hoard ivere ivhite, all on the other orange.'''' 



