269 Part II I. — Seventeenth Annual Report 



in tow-net gatherings from the Clyde — the only Scottish locality where it 

 has as yet been observed. The form referred to, which in general appear- 

 ance is not very unlike the widely distributed crustacean known as 

 Lucifer, has been known for a considerable period ; it was described 

 and figured under the name of Trachelifer, by the late Mr. George 

 Brook in 1888*, but is evidently immature, and there is still 

 some doubt as to the species to which it really belongs. The neck 

 of this young form is long and slender ; the thorax is small, and is 

 furnished with more or less rudimentary appendages ; the slender 

 abdomen is more than twice the length of the neck, and the last 

 abdominal segment is as long as all the other segments of the abdomen 

 put together ; the telson and uropods are comparatively short, and more 

 or less rudimentary. Figure 16, PI. XII. , represents one of the Clyde 

 specimens, which measured overall about 16*5 millemetres (§ of an inch). 

 The specimens that have been observed vary in length to a small extent, 

 but all possess the same slender Lucifer-like form. 



Habitat. — Station VII., Firth of Clyde. (I have also a specimen from 

 Loch Fyne collected in 1886.) 



Additional Remarks. — Figures 17 to 20, Plate XII., exhibit on a some- 

 what enlarged scale portions of the Lucifer-like crustacean referred to above. 

 In fig. 17, which represents the front part of the cephalic segment, the eyes 

 are large and somewhat divergent; the triangular rostrum is slightly shorter 

 than the eyes ; both pairs of antennae are slender and elongate ; the 

 antennal scales are also slender and rather shorter than the basal part of 

 the antennules. Fig. 18 represents what appears to be one of the first 

 peraeopods. In the specimen dissected this was the only pair that 

 had the extremities of the principal branches chelate ; all the other trunk 

 legs appear to be simple. Fig. 19 represents one of the first pair of 

 abdominal appendages, which are all more or less rudimentary : each 

 appendage consists of a single unjointed branch, with a furcated 

 extremity. Fig. 20 represents the posterior end of the last abdominal 

 segment, together with the uropods and telson ; the appendages of the 

 last abdominal segment form tapering and slightly curved processes; the 

 uropods are foliaceous, and little more than half the length of the telson ; 

 the telson is comparatively of large size. In the specimen dissected for 

 drawing, the telson was somewhat imperfect. The extremity is therefore 

 indicated by dotted lines, but in another specimen in which the telson 

 was fairly perfect the following characters were observed : — The terminal 

 lateral processes had each two small teeth on the inner margin, and the 

 part between the lateral processes was furnished with twenty-two short 

 and slender marginal spines ; the two middle spines were rather shorter 

 than the others ; and there was a slight but perceptible gradation in the 

 length of those on each side of the two central ones, the spines nearer 

 the centre being somewhat shorter than those more distant. The larva 

 above referred to was described by Claus as eine in vieler Hinsicht merk- 

 wurdigen Larve in a paper Zur Kenntniss der Kreislaufsorgane der Scliizo- 

 poden und, Deeapoden, in Arb. d. z. Inst. Univ. Wien. V. 1884, p. 302 

 (32), PJ. VIII., figs. 48-50. The same writer subsequently described a 

 somewhat more advanced specimen as the larva of Calliaxis adriatica, 

 Heller, ibid. VI. 1886, p. 63, PI. V., fig. 45. The identity of Brook's 

 Trachelifer with Clauses Calliaxis — larva is pointed out by Korschelt 

 and Heider, Lehrb. d. vergl. Entwicklungsgesch. d. wirbell. Th., I., 

 p. 471. Calliaxis is not yet known as a British form, being only known 

 from the Adriatic and from Naples : at the latter station the larva is met 

 with in the surface-fauna, but the adult has only been found once in 25 

 years (S. Lo Biauco, Mitth. Zool. Stat. Neapel. XIIL, p. 503, 1899). 



