I. '08. 



103 



The three species found off the Irish coast yield the follow- 

 ing branchial formula : — 



i vn. 



! 



vin. 



TX. 



X. 



XI. 



XTT. 



xin. 



XIV. 



Podobrauchiae, 



ep. 



l + ep. 



ep. 



ep. 



ep. 



+ ep. 





... 



Arthro branchiae, 



... 















... 



Pleurobranchiae, 









1 



1 



1 



1 



1 



Spirontocaris Gaimardi (H. M.-Edw.) i = Hippolyte pandali- 

 formis, Bell) has been recorded in British waters from the 

 Firth of Forth and off Aberdeen (Scott) and from various 

 localities on the west coast of Scotland (Scott, Bell, etc.) ; it 

 has also occurred in abundance off the Shetland Is. (Norman), 



Spirontocaris polaris (Sab.) ( = Hippolyte cultellata, Nor- 

 man) has, within the British Area, been recorded only from 

 the neighbourhood of the Shetland Is. (Norman, 1867). 



Spirontocaris spinus (Sowerby). 

 PI. XIV, fig. 1. 

 Hippolyte spinus, Bell, 1853, fig., p. 284. 



S. spinus, var. Lilljeborgi (Danielssen). 



PL XIV, figs. 2-10. 



Hippolyte Lilljeborgi, Danielssen, 1859. 



Hippolyte securijrons , Norman, 1862. 



Spirontocaris spinus, Spence Bate, 1888, Pis. cvi. and 



CVII. 



Hippolyte securijrons , Appellof, 1906. 

 Spirontocaris Lilljeborgi, Hansen, 1908. 



It has always been rather a doubtful question whether S. 

 Lilljeborgi is a distinct species from S. spinus or merely a 

 variety of it. The evidence which has so far been produced 

 inclines me to the belief that only one species and a fairly well 

 marked variety are represented in the N.E. Atlantic, although 

 in some localities one of the forms appears to exist to the ex- 

 clusion of the other. The two forms may usually be sepa- 

 rated thus : — 



S. spinus, typical. 



Dorsal teeth extending to 

 the extreme posterior edge of 

 the carapace, often finely ser- 

 rate on their upper margins. 

 Third abdominal somite pro- 

 duced posteriorly as a stout 

 tooth over the succeeding 

 somite. 



S. spinus var. Lilljeborgi. 



Dorsal teeth not extending 

 as far as the posterior edge 

 of the carapace, their upper 

 margin usually smooth. 

 Third abdominal somite not, 

 or only slightly, produced 

 over the succeeding somite. 



