12 COLD SPRING HARBOR MONOGRAPHS. VII. 



Variations in C. Signatiis, var. Anniilicornis. — In the fourth 

 swimming feet I have recorded five cases in which "a tiny seta" 

 is present in the distal position on the inner margin of the distal 

 segment of the inner ramus, and four cases in which this position 

 was occupied by "a tiny bunch of hairs." Sometimes only two 

 or three hairs are present. 



In the outer ramus of the first foot, I have observed an interest- 

 ing case of variation, similar to the one noted in C. atcr, where a 

 seta has given place to spiny serrations on its outer margin. The 

 outer apical spine has become modified in this case, so that on its 

 outer side it is clearly a spine; while on its inner side it is as 

 clearly a seta. Such instances show the ease with which a spine 

 and a seta may become interchangeable, and throw doubt on the 

 value of these structures as organs of specific value. 



The synonymy of the two forms that I have in this paper 

 designated as C. signatus coroiiatus and C. signatns annulicornis 

 is very complicated. Herrick (1895) regarding annulicornis as 

 synonymous with tcniiicornis, recognizes only the varieties coroiiatus 

 and teniiicornis. His diagnosis is as follows: He states that the 

 two varieties have similar armature on the swimming feet, but that 

 tenuicornis differs from coroiiatus in the absence of serrations on 

 the antennal lamellae and in the divarication of the ovisacs. Now, 

 as stated above and as shown by a comparison of Figs. 7 and 4 

 (Plates II. and I\^.), there is typically a difference in the arma- 

 ture of coronatiis and annulicornis {tenuicornis Herrick). The 

 antennal lamella of annulicornis sometimes bears serrations (Plate 

 IV., Fig. 5) and coronatus sometimes bears its &gg masses in a 

 divaricate position, as I have found in attempting to distinguish the 

 two forms by this character. Consequently Herrick's diagnosis is 

 untenable. Marsh also recognizes the distinctness of the two 

 forms, which he describes under the names C. fuscus and C. albidus, 

 JuRiNE : earlier names given to corresponding European species. 

 The form designated C. gyrinus by Forbes is undoubtedly annuli- 

 cornis. 



While all of the forms of the signatus type that have thus far 

 been encountered in Long Island waters have been unequivocally 

 either coronatus or annulicornis, nevertheless there are wide ranges 

 of variability in the reduced seta on the inner ramus of the fourth 

 foot of annulicornis and in the hyaline plate of the antennai of 



