254 University of California Publications in Zoology. [Vol.8 



ties, temperature, and currents delimit the seasons and spawning 

 territories of the adults of the various species of the Gadidae. 



Distinguishing characters of a type not unlike in essential 

 nature to that found among the Gadidae may also be demon- 

 strated between the various species of Gonyaulax. It will suffice 

 for illustration to compare two common species, G. spin if era and 

 G. polygramma (compare figs. A-D, pi. 16, fig. 39 and pi. 17, 

 fig. 47), species of about the same size, often found in the same 

 waters. They differ in size, proportions, in displacement, over- 

 hang and margins of girdle; in proportions, shape and markings 

 of the ventral area ; in shape of apical region ; in size, number, 

 and symmetry of antapical spines ; in location of ventral pore ; in 

 shape of plates 1\ 3', 6", 6"", P', and i""; in surface markings 

 which are predominantly linear in polygramma, and reticulate in 

 spinifera. Finally in numbers and distribution there are indica- 

 tions (precise information is lacking on account of confusion in 

 literature as to the synonomy and specific limits of G. spinifera) 

 that G. spinifera has more of a neritic distribution in colder 

 waters and G. polygramma oceanic in warmer waters. 



The number of characters separating species would be some- 

 what lessened if the comi)arison should, for example, be made 

 between those of the polygramma series, as for example G. tur- 

 hynei (pi. 17, fig. 44), G. polygramma (pi. 17, fig. 47), G. liofoidi 

 (pi. 14, fig. 80), and G. pacifica (pi. 16, fig. 35), but even here 

 the characters found in connnon in all or certain members of the 

 series such as linear markings, antapical spines, antapical asym- 

 metry, or apical horn, differ between several members of the 

 series in the degree and manner of their expression in qualitative 

 and quantitative fashion. 



II. CHARACTERS OF VALUE IN DISTINGUISHING SPECIES 

 1. Structural Characters 



Those structural characteristics which have proved to be of 

 greatest value in the analysis of species in Gonyaulax fall natur- 

 ally into two groups, ( 1 ) those affecting fundamental features 

 such as number of plates, form of the body, displacement of the 

 girdle, and form of the ventral area; and (2) superficial char- 



