I. '08. 5 



species found off our coasts ; in order to give them a somewhat 

 wider application, species found in British waters, but not 

 up to the present known from Ireland, have been included 

 with a brief note on their distribution. 



All Irish species discovered since Bell's monograph of Bri- 

 tish Decapods was published (1853) have been described and 

 figured^. The synonymy of many of the species has been 

 fully treated by recent authors, and it has not been thought 

 necessary to repeat it here ; in the majority of cases references 

 will be found only to the more important papers. 



The descriptions of colour were drawn up from notes taken 

 from living or freshly caught specimens on board the Helga. 

 Among littoral and shallow-water forms great variation is often 

 found, and in such cases notes based on the examination of 

 at most a few specimens probably do not convey an adequate 

 idea of the different phases of colouration to be met with ; the 

 case is different in deep-water species, which do not, as a rule, 

 show any marked divergence from a standard type. 



During the course of townetting observations a large col- 

 lection of larvae has been acquired. The vast amount of time 

 which would be required for a full treatment of this material 

 prohibits its inclusion in the present paper, but it has been 

 found possible to discuss a few deep-water larvae which could 

 be definitely traced to adult forms. 



In dealing with all except the commonest species the actual 

 records are given. The temperature and salinity of the water 

 are now regarded as having an important bearing on questions 

 of distribution, and consequently such data, where available, 

 have been appended to each station ; it is hoped that this 

 method, though rather cumbrous, will be found of greater ser- 

 vice than mere reference to lists published separately. In 

 treating of specimens caught in midwater, temperature and 

 salinity are given for the surface as well as for the greatest 

 depth fished, as it is impossible to be certain that the speci- 

 mens were not caught during the ascent of the net. 



The positions are to be regarded as the approximate central 

 point of each haul. Soundings were, as a rule, taken at the 

 beginning and end of each station ; both are given, and it will 

 be noticed that in a few cases, in deep water on the Atlantic 

 slope, the two differ widely, owing to the comparatively rapid 

 shelving of the sea bottom in those particular localities. 



Unless otherwise stated, measurements of all specimens are 

 given in mm. from the apex of the rostrum to the tip of the 

 telson . 



According to the views of the committee which sat in 1890 

 the western limit of the British area coincides with the 1,000- 

 fathom line. All the species hereafter noticed have been 

 found within this area. On a few occasions midwater nets 

 were fished from the Helga outside this western limit ; speci- 

 mens caught at such localities do not seem to call for separation 

 from the rest, for it is obvious that there is no natural faunistic 



1 With the exception of some Pandalidae, which have been very fully 

 dealt with in recent years by Caiman (1896). 



