84 



Papers from the Department of Marine Biology. 



There are also a number of cases in which the rostrum is deflexed. 

 From the comparison here made and the facts stated I think there is 

 little doubt that we are dealing with one very variable species. 



I have compared my collection with the full description given by 

 Balss of his specimen (the fullest description given of (7. elegans) and 

 find the following discrepancies: 



(1) In the third maxilliped the merus is armed with three prominent 



spines on the internal border in the Japanese form, in mine with 

 only two; Henderson and Ortmann both describe G. elegans 

 with two spines in this position. 



(2) In the ambulatory limbs the merus has a spinose upper angle accord- 



ing to Balss, but is smooth in the Torres Straits forms; the 

 dent i dilation of the dactylus is weak in the former, but in the 

 latter there is a powerful end claw, succeeded by prominent teeth 

 only gradually decreasing in size. 



FIG. 4. Galathea. 



A. G. elegans, Torres Straits, rostrum showing lateral teeth and arrangement 



of hairs. X 8. 



B. G. minuta, third maxilliped, showing spines on merus (m). X 18. 



C. G. in-flat a, third maxilliped. X 4. 



But in a variable species we might expect to find such differences. 

 The Japanese form described by Balss is clearly a rather extreme mem- 

 ber of the variable series, as shown by the fact that it has the highest 

 number of denticulations on the rostrum recorded. The agreements 

 between Balss's description and my specimens outweigh the differences. 



In conclusion, I give the following diagnosis, to embrace all the forms 

 here discussed: 



G. elegans: Rostrum rather more than half the length of the remainder of 

 the carapace with from 5 to 9 small denticulations on each side; width about 

 half the length; sometimes deflexed; carapace somewhat pear-shaped; about 

 a dozen indentations on each side; surface traversed by many narrow hori- 

 zontal furrows, from which spring thick lines of short fine hairs, though these 

 may be absent or nearly so. The rostrum is covered with hairs rather longer 

 than those on the carapace, arranged in distinct crescents posteriorly. Dor- 

 sum and limbs covered with dark pigment, but there are generally pigment- 

 free longitudinal bands of variable width. ChelsB long and slender, cylin- 

 drical in section, thicker in the male than the female, varying in length in 

 the latter. 



Often, if not always, commensal with crinoids. 



