CRUSTACEA MALACOSTRACA. 



comparatively speaking not thin, and are divided into several joints; also the very long setse on the 

 outer margins of the first to the fourth pair and the apical and subapical setae on the fifth pair are 

 placed on protuberances as on a kind of basal support. The characteristic distribution of the setse and 

 the relative position of the setigerous groups on the inner branches can be seen from the figures. 

 The females with marsupium measure 16 17 mm., the males 13 mm. in length. 



Family Petalophthalmida. -- In 1887 I founded this species under the name Arctomysis Fylla- 

 n. gen., n. sp. and wrote: "I believe that my new genus should be placed near the genus Pctaloph- 

 thalmus Will.-Suhm and that these two genera should form together a family by themselves within the 

 order of the Mysidae". In 1893 Stebbing gave it the name Hansenomysis, as the generic name used 

 by me had been applied by Czerniavsky to a genus which was, however, quite unmaintainable (see 

 below p. 102). In 1895 Faxon described in detail two genera founded by him in 1893 and thus writes: 

 ^Petalophthalmus, Scolophthalmus, Hansenomysis, and Ceratomysis, form a natural group of genera 

 characterized by the development of seven pairs of incubatory lamellae in the female (the anterior pair 

 sometimes rudimentary), the absence of an exopod from the maxillipeds, the outgrowth of a large, 

 porrect lobe from the inner margin of the merus of the gnathopods, and the imperfect development of 

 the carapace, which leaves the last two segments of the cephalo-thorax free". Seven pairs of marsupial 

 lamellae are also found, as Faxon also remarks, in Borcomysis, but in no other genus of this suborder, 

 where only three or fewer pairs of lamellae are met with; on the other hand, the other characters 

 summed up by Faxon are exclusively peculiar to the genera named, which I therefore unite into one 

 family with the title as above 1 . This family further differs from all other genera of the suborder by 

 the great difference existing between the terminal portion of the second to the fourth pair of thoracic 

 legs and that of the fifth to the seven pair, the last three pairs having the seventh joint and the 

 claw fused together to form a long claw, whilst the same parts in the second to the fourth pair are 

 very short and concealed in setae. -- The genera of the family further show great agreement with 

 one another in several respects, such as, the carapace has well-marked furrows on it, the outer ramus 

 of the uropods has a very distinct articulation at a little distance from the tip, etc. 



Of the four genera Petalophthalmus and Ceratomysis have a long, good-sized process from the 

 fourth articulation of the maxillipeds and this process is lacking in the other two genera. Pcfalopli- 

 thalmus differs greatly also from the other three genera by the mandibular palp being very much 

 elongated and by the unusually reduced and characteristic pleopoda in the male. I mention this last 

 character as I am acquainted with the hitherto undescribed male of Ceratomysis, and Scolopltthalmus 

 is so nearly related to Hansenomysis that the pleopods are probably almost the same in these two 

 genera. Further, the outer branch of the antennules in the male is not thickened in Petalophthalmus, 

 whereas it is greatly thickened in Ceratomysis and as in Hansenomysis and presumably in Scolopli- 



1 In the above-named paper (Fisheries, Ireland, Sci. Invest 1904, V., [1906]) Holt & Tattersall established this family. 

 and their diagnosis comprises the major part of the features mentioned here by me. But when I received their paper this 

 portion of my manuscript was already translated; for that and other reasons I prefer to alter nothing in my own text, only 

 referring the reader to their paper. I will add, that the family must, of course, bear the name of the authors, as their paper 

 has been published years before mine, and that their diagnosis contains a correct character not pointed out by me, viz. 

 "Inner uropods without otocyst". 



