I. '08. 104 



Off the Scandinavian coasts these two forms seem to be 

 well marked and restricted to different localities and authors 

 who have recently dealt with the Natantia of these districts 

 regard them as two distinct species (WoUebaek, 1900, and 

 Appellof, 1906). Appellof, however, has put the case very 

 clearly and refers to the capture of the two forms together 

 near Iceland ; on this occasion a few intermediate examples 

 w^ere also obtained. 



The majority of the specimens caught by the Challenger 

 expedition off the east coast of North America and described 

 by Spence Bate^ (1888) may be referred to the var. Lilljehorgi, 

 but his var. n appears to be somewhat intermediate in 

 character, with the teeth continued far back on the carapace 

 and wdth some of them serrate on their upper margins. 



Miss Eathbun (1906) has recently dealt with specimens 

 from the Pacific coast ; S. spinus is retained as distinct from 

 S. Lilljehorgi (though without definitions) and several other 

 extremely closely allied forms serve as the types of new 

 species. It is difficult to see what useful end is attained by 

 the erection of species founded on such exceedingly fine dis- 

 tiiictions in a group w^ell know^n for its very wide variation. 



Typical forms of Spirontocaris spinus are of very rare occur- 

 rence off' the British coasts, and the var. Lilljehorgi, although 

 rather more frequently found, is also scarce and local. Of 

 the specimens obtained in Irish waters, all except one are re- 

 ferred to the variety. In this one example (fig. 1) the teeth 

 are continued rather far back on the carapace, but show 

 no trace of serration, w^hile the posterior margin of the third 

 abdominal somite is very strongly produced. 



In the remaining specimens the teeth, w^hich also show no 

 trace of serration, are not continued so far back on the cara- 

 pace, and the third abdominal somite is not produced pos- 

 teriorly (fig. 2). 



The shape and dentition of the rostrum are more variable in 

 this species than in any other known from British waters and 

 the character is consequently of little value as a distinction 

 between the two forms; but the type with a deep emargina- 

 tion immediately below the apex (fig. 1) is only rarely met 

 with among examples of the var. Lilljehorgi. 



Size. — The largest specimen found off the Irish coast is a 

 female measuring 40 mm. ; Ohlin (1902) records a specimen 

 62 mm. in length. 



Colour in life (of the var. Lilljehorgi). — The carapace and 

 abdomen are bright red, dark red or dark purplish brown, 

 usually mottled and often with a sprinkling of very small 

 white or pale yellow chromatophores. The sides of the cara- 

 pace and pleura are, as a rule, much darker than the dorsal 

 colouring. Rarely, a subquadrate white patch occurs on the 



1 Spence Bate's figures (pi. cvii.) of certain appendages of this species 

 fall rather below his general standard of inaccuracy; it is hoped 

 that figs. 6-10, PI. XIV, will be found a trifle less misleading. 



