130 DR. G. HERBERT FOWLER ON THE [Feb. 3, 



that this family takes its origin very near to the root of the 

 Decapodan stem, and that it has far closer affinities with the 

 latter than with the Mysidse. In N't, tiphanes 1 and Euphausia 2 , 

 and possibly in other genera also, the youngest Calyptopis-l&YvsQ 

 show seven spines on each side of the telson ; unlike all other 

 Schizopoda, so far as is known, except perhaps Lophogaster, they 

 are thus in absolute accord with the " urspriingliche Borstenzahl 

 7 + 7" which Mayer attributes to the primitive Macruran and 

 Brachyuran. In Euphausia, Nyctiphanes, Thysanopoda, and 

 Nematoscelis according to Sars (op. cit.), and in Thysanoessa, 

 the number is increased at later stages by a median terminal 

 spine, which, like the others, is jointed to the telson. Accepting 

 Mayer's enumeration of the spines from the middle line outwards, 

 and styling the median azygos spine of the Euphausiidse as 0, 

 spines 7 are found in the adult Thysanoessa about one-third of 

 the length of the telson from the root ; spines 6 at about two- 

 thirds of its length from the root ; spines 5 are lost ; spines 4 

 persist as the large lateral jointed spines near the end of the adult 

 telson 3 ; and spines 3, 2, 1, disappear altogether in the course 

 of development. On page 131, I have illustrated four stages in 

 this reduction omitted by Sars, of which fig. 15 does not quite 

 bear out his description : these show the disappearance of the 

 median spine 0, and the commencement of a new unjointed 

 growth of the telson backwards, to form the lanceolate tip of the 

 adult. The character of the telson and the presence of this 

 median spine will apparently form a good criterion for the 

 separation of Euphausidan larvae (at stages later than the Meta- 

 nauplius) from other Schizopodan and from Decapodan larvae. 



The earliest Calyptopis-l&rvsd captured by the ' Research ' 

 resembled closely those figured by Sars (op. cit.) for other genera, 

 except for the facts that the carapace was much more globular 

 anteriorly and was devoid of spines or processes. 



NYCTIPHANES NORVEGICA M. Sars. 



This form was captured on only six occasions. Although a 

 North Atlantic type, it is not an essentially Arctic type like 

 Thysanoessa longicaudata : it is of constant occurrence in certain 

 localities on our own coasts, and has been recorded from as far 

 south as Portugal. The various records of its occurrence are cited 

 by Canon Norman 4 , but unfortunately the size of the individuals 

 and the depth from which they were derived are only rarely noted. 

 I am informed by Sir John Murray that, in his experience, large 

 adult specimens are taken only in deep water. 



1 G. 0. Sars : Chall. Rep. Zool., xiii. Schizopoda, pi. xxvii. fig. 6. 



2 C. Glaus : Untersuch. Crustaceen-Systems, pi. i. fig. 2, Wien, 1876, 4to. 



3 With regard to these, Boas (op. cit. p. 623, note 5) has suggested that they may 

 be homologous with the long caudal appendages of Nebalia and many Phyllopods. 

 This possibility is rendered considerably more remote by their being merely two 

 persistent spines out of a series which is not represented in the forms cited by him. 



4 A. M. Norman : Ann. Mag. Nat. Hist. (6) ix. pp. 459-460 (1892). 



