FAUNA OF THE OUTER WESTERN AREA OF THE CHANNEL. 345 



In referring the examples recorded to the species cincinnatus more 

 importance has been attached to the character of the gills, which are 

 present without exception on two segments only, than to the uncini, 

 which are very variable in form. The specimens range from young 

 examples of about 12 mm. in length to large ones of 10 cm. Between 

 such extremes the only noticeable difference in the uncini is one of 

 size. The irregularity of form occurs in both, though the range of 

 variation seems greater in the larger specimens. The uncini conform 

 on the broad lines with the description and figure of de St. Joseph 

 (103), but often differ much in detail. 



Eegarding the uncinus from the face and tracing it from below 

 upwards, there is first (a) the large central tooth, or " great fang," so 

 termed by Mcintosh. Above this (b) are usually two, but very often 

 three, strong teeth, of which the central one, when present, has a 

 slightly higher origin than the laterals. Next follows (c) a range with 

 two small lateral teeth and one larger central one. This central tooth 

 is the homologue of the large central tooth in the (b) range, and when 

 present in the latter it is therefore absent from the range above in the 

 reckoning adopted, and the (c) range then has the two small laterals 

 only. Finally (d) occurs a range of very small teeth, about three to 

 five in number, which fill in the apical space. These occasionally 

 extend around the apical margin of the uncinus, so that their two 

 extreme laterals lie one on either side of the (c) range, and the latter 

 then appears to possess altogether five teeth, or four as the case may 

 be. In a preparation of a young specimen of 18 mm. in length, the 

 condition with three teeth in the (c) range is the most frequent, while 

 apically the arrangement is much confused, and the remaining teeth 

 are crowded together with little appearance of order. It must be 

 added that the use of the term " range " is quite artificial, all of the 

 teeth lying closely apposed, so that any irregularity occurring is liable 

 to confuse the scheme of arrangement considerably. 



In the profile view a difl'erence occurs from the figure by Malmgren 

 (94), which shows the uncinus rather narrower in antero-posterior 

 measurement, and with the apex simply rounded and without the 

 slight projection where the extreme apical teeth are borne. Malm- 

 gren's figures are as a rule so true to life that this difference presents 

 some difficulty. The second point, however, is involved in Marenzeller's 

 figure of the species (96), where the apical projection is distinctly 

 shown. From the description of the species by Marenzeller and de St. 

 Joseph the only important discrepancy is the frequent enlargement of 

 the central tooth in the (c) range and its extension as a third tooth 

 into the range immediately below. This character, which is not men- 



NEW SEKIES. — VOL. IX. XO. 3. JUXE, 1912. Z 



