OPISTHOBRANCHIATA FROM THE ABROLHOS ISLANDS. 545 
It does not appear to agree with any previously recorded species, and so 
is described here as new with the name Spluernstoma dakeni, after my friend 
Professor W. J. Dalvin, who collected it. 
Family HEXABEANCHID.E. 
This family contains only one genus, and its characters are those of the 
genus. 
Genus Hesabranchus Ehrenberg, Symb. Phys. (1828). 
Type by monotypy : 11. prcetextus Ehrenb.^ pi. 1. figs. A-0. 
N.B. — The platfts in this work were published in 1828 and the text 
in 1831. This form appears on the plates. 
The body is large and of an elongate-oval shape : the back is smooth 
and broad. It passes out laterally to a folded margin, which is continued 
out as the enormous sheet-like much folded mantle, which may be wider 
than the body. The branchial plumes, generally 6-8, are dendritic and 
distinct, and arranged in a circle around the anus. They are not retractile, 
but contractile, and their bases are surrounded by a shallow wide-open 
depression. The rhinophores have a cylindrical stalk and a perfoliate clavus 
set at an angle to it. The oral tentacles are large and auriculate with a 
folded margin. The foot is relatively well developed. The labial armature 
is well developed and composed of tiny hooked spines. The radula is well 
developed, with no rachidial tooth, and the pleui'al teeth are numerous, 
hamate, and liave no lateral denticles. The penis is long and unarmed. 
Only the posterior blood-gland is present. Bergh classes these as a 
sub-family of the Dorididfe Cryptobranchiatse. This name cannot stand, 
and the forms are not even (hyptobranchiate. They are here raised to a 
separate family. 
Species Hexabranchus imi'erialis Kent, Nat. in Austr. 1897, p. 150. 
(PI. 28. fig. 11 ; PI. 29. figs. 41-44.) 
Body. The body is moderately stout, of an elongated oval shape, and the 
skin is smooth. The most striking feature, however, is the mantle, which is 
extraordinarily well developed and takes the form of a thin wide flanoe, 
wider than the body, passing all round save at the anterior end, where it is 
only narrow. The rhinophores with their sheaths stand up prominently at 
the anterior end, and the circle of gills is conspicuous at the hinder end. 
Colour. The colour of the preserved specimens is a dull greenish o-rey 
without any indications of markings. Professor Dakin say^s it is identical 
with Saville Kent's drawing, and that at a distance it looked not unlike a 
great piece of fresh lung torn from a vertebrate. Kent figures it as of 
a flaring red colour all over with no markings. 
Dimensions. The body of the largest specimen measured 125 mm. long 
by 50 mm. wide and 44 mm. high. Beyond this the mantle extended 80 mm. 
along each side, 45 mm. across the posterior end, iind 6 mm. across the 
anterior end as a sort of oral veil. 
LINN. JOUEN. ZOOLOGY, VOL. XXXV. 39 
