"Ti^r- 



__^^ n_LLn^ - 



118 



STALK-EYED CRUSTACEA. 



F" 



are hardly distinguishable. It follows that unless the adult male be known, a 

 species cannot be referred to its proper genus in Bate's system. That author 

 was most arbitrary in the disposal of his own species, for three of those 

 which he placed in Pcntacheles, viz. ohscitrus, Icevzs, and gracilis^ were known 

 to him only through the female. Keeping the above-mentioned facts in 

 view I have deemed it advisable to unite Fentachelcs and Folycheles^ provision- 

 ally at least. For similar reasons I have not recognized Bate's genus Slereo- 

 mastis, which was instituted in 1888,* for the reception of two species which 

 lack epipods on the thoracic appendages, but in all other respects agree with 

 Pentacheles. An examination of a large number of species discloses a gradual 



r 



transition in the development of the epipods, from large well developed or- 

 gans through small, delicate and thin ones, to merest rudiments in the shape 

 of small expansions at the base of the stem of the gill. 



Furthermore, a nomenclatural difficulty confronts him who treats of 

 this family, arising from our imperfect knowledge of the structure of the 

 eye in P. typMops Heller, the type of the genus PolycMcs. In Polycheles o{ 

 this report {^ Poly cheles + Pentacheles -^ Slereommtis of Bate) the ophthalmic 

 lobes are lodged in a deep notch or sinus of the anterior margin of the cara- 

 pace and send off from their anterior portion a long cylindrical process 

 beneath the anterior lateral angle of the carapace. 



In Willemoes 



W. lerdodacMa W 



/ 



and is not lod^^-ed in a sinus of the carapace, nor does it send off a process 

 beneath the anterior lateral angle of the carapace. Of Polychclcs lyphlops 

 Heller says :t "Die Augen fehlen fast ganz, nur an dcr Basis der oberen 

 Antennen gewahrt man an der Stelle, wo sich der Stirnrand nach unten 

 umbiecrt zwei schwarze rundliche Flecken als Eudimente derselbcn.'' This 

 description applies more nearly to the eye of Willemoesia than to that of Poly- 

 cheles of Bate and more recent authors.:}: On the other hand, the notch in 

 the anterior margin of the carapace, although rather shallow, and the gen- 

 eral character of the carapace as shown in Heller's figure, indicate a' species 

 con^'-cneric with those which have since been placed in Polychelcs, Should a 

 re-examination of the type of Polychclcs lyphlops reveal an eye constructed as 



* Rep. Challenger Macnira, p. 154, 1888. 



f Sitzungshcr. Kais. Akad. Wisscnsch. Wien, XLV., Ahili. I., 390, 18G2. 



X In Willemoesia the posterior tlioracic feet are chelate in both sexes, while in the type specimen of 

 P. typMops (a male) these appendages are simple. But much stress cannot be laid upon tliia dilTcronce, since 

 Heller's unique specimen of P. ti/phlops wns only Wo inches in length. Norman's description of P. iypldop^ 

 (Ann. Mag. Nat. Hist., 5th Ser., IV., 176, 1S79) lias no bearing on the point here under conyideratlon, .since 

 it is very doubtful whether the specimens described by him are the same as Heller's species. 



