GENERA UEOTHOE AND ITJiOTHOIDES. 7 



Boeck's description in having the angles of the third pleon-segment acute (though not 

 produced upwards), and in ha^'ing the first joint of the third perseopods rather less 

 dilated than is usual in the genus, and with the lower hinder angle of the joint very 

 much rounded. In Boeck's work, De Skand. og Arkt. Amphip. plate vii., fig. 4 n pro- 

 bably refers to these limbs, not, as the lettering would indicate, to the fifth perteopods. 

 In describing the fifth perseopods he says that the fourth joint is longer and thicker than 

 the Jirst. First is obviously a misprint for Jifth, a correction which brings the statement 

 into agreement with Norman's specimens above referred to, and with Boeck's own figure 

 of the limb, plate vi. fig. 9 m, where 9 m would indicate the third or the fourth perseo- 

 pods, and is beyond doubt a mistake for 9 n. Plate vii. has two figures marked 4 h, as if 

 representing the maxillipeds of Urothoe norvegica, but the upper one should probably 

 be 5/j, referring to the species ^' Phoxus HolhdUi;" in the lower one the first joint of 

 the palp has been accidentally omitted. The figures 4 g and 4 tn near the right-hand 

 lower corner of the plate are most likely also wrongly numbered. 



In 1862 Spence Bate described and figured under the title "'Urothoe Bairdii, n. s.," 

 a specimen obtained, like Urothoe marinus, from the Moray Firth. The lower antennas 

 show that the specimen was a male, but not a male which had attained its fullest 

 development, so as to have calceoli and a very prolonged flagellum with very slender 

 joints. Both in the Museum ' Catalogue' and in the 'British Sessile-eyed Crustacea' 

 the maxillipeds are figured, evidently by mistake, without a finger ; in the latter, but 

 not in the former, work the lettering of the first and second pairs of uropods is 

 transposed. The latter work affirms that the third persopods " terminate in a knife- 

 shaped finger, the anterior margin of which is entire," and the margin is so represented 

 in both works, owing, I believe, to defective observation, since the denticulation of this 

 margin may easily escape notice from some points of view, but has nevertheless proved 

 to be present in all specimens of the genus that I have examined. It seems to me 

 scarcely doubtful that Urothoe Bairdii is a synonym of Urothoe marinus. The pecu- 

 liarity of having the outer ramus of the third uropods devoid of plumose setee can 

 scarcely be relied on of itself to constitute specific distinction. It can derive no validity 

 from the sanction of a single, not fully developed, specimen. Boeck supposes Urothoe 

 Bairdii to be a synonym of his own Urothoe norvegica ; but in the former species the 

 first joint of the third perseopods is very broad instead of being, as in Boeck's species, 

 comparatively narrow, and the rami of the first uropods are very unequal, while in 

 Boeck's species they are equal, so that there is really no question of uniting these 



two names. 



In the same year (1862) Spence Bate established another species, upon a specimen 

 one-tenth of an inch in length from Tenby, under the name Urothoe hrevicornis, n. s. 

 The specific name is unfortunate, since it is now known that the young and females 

 in all species of the genus have the lower antennae short, while they are long in the 

 adult males. As in the case of Urothoe marinus, so here it is evident that the first and 



