99 



divergent strengthening ribs on the outer branch, and a single 

 midrib on the inner, which bears a row of small spines. 



Each gill has the form of an axis which gives off rows of slender, 

 somewhat flattened processes, which all lie in one plane, and 

 decrease in size towards the tip of the axis. 



The branchial formula is as follows : — 



— VII. VIII. IX. X. XI. XII. XIII. XIV. 



Podobranchs. 1+ep. 1 +ep . 1 +ep . 1 +ep . 1 +ep. 1 -j-ep. ep . — 



Arthrobranchs — 122222 — 



Pleurobranchs . — — — — — — — — 



Size. — The single Irish specimen measures 41 mm. Two 

 specimens from the Adriatic measure 42 mm., and 49 mm. 



General Distribution. — The species is found most plentifully 

 in the Adriatic, specimens from which were described by 

 Heller and Nardo. It appears to be extremely rare in the 

 other parts of the Mediterranean. Lo Bianco says it has 

 been taken only once in twenty -five years in the Bay of 

 Naples, though the larval form, the peculiar free-swimming 

 stage known as Trachelifer, is frequently found there from 

 May to Septem.ber. So far as I know no adult specimen had 

 been taken outside the Mediterranean until the single Irish 

 specimen was taken in the Irish Sea in 1905. ^ Dr. Scott in- 

 forms me that an adult specimen was taken by the Scottish 

 Fishery Board cruiser, Goldseeker, in Loch Fyne, in 1908. 

 Though these are the first two adult specimens to be found 

 in British waters, fragments of Jaxea were found in fish taken 

 near Ailsa Craig, in the Firth of Clyde, in 1899 (Scott, 1899). 



The larval form, Trachelifer, has been taken with considerable 

 frequency in the Irish Sea, and on the west coast of Ireland 

 and Scotland. It is found fairly widely distributed in the 

 Mediterranean. 



Irish Distribution. — Only a single specimen, an adult male^ 

 has been found within the Irish marine area. 



Helga. 



S. 259.— 21 II '05. 13 mis. off Clogher Head, Co. Louth, 

 32 J fms., mud. Trawl. — One, 41 mm. 



Vertical Distribution. — The Irish specimen was taken in 

 32j fms., and the Scottish in 34 fms. 



^ I have compared the Irish specimen with several from the Adriatic, which were 

 sent to me through the kindness of Prof. Steuer of Innsbruck, and find complete 

 agreement in all the characters. 



