DESCRIPTION OF SPECIES. 
Myzostoma , F. S. Leuckart. 
1. Myzostoma horologium , n. sp. (PI. I. figs. 1-17). 
This form, of which I was able to investigate a great number of examples, closely 
resembles our European form, Myzostoma glabrum, but has not the central muscular mass 
so highly developed. The dorsal surface is generally flat or somewhat vaulted and bent 
upwards at the margins. The diameter of the body in the largest specimen was 6 mm. 
The skin of the back has no conical papillae like those of Myzostoma glabrum, but merely 
some irregular wrinkles, and these only in large specimens. Cirri are entirely wanting. 
The pigment is arranged in much the same fashion as in Myzostoma glabrum ( cf. , Genus 
Myzostoma, pi. i. figs. 2-10), but there is only a single median longitudinal line instead 
of two, which, however, differs considerably in different individuals. The typical 
coloration is shown in fig. 4 ; it resembles very much the dial of a watch divided into ten 
parts with two large hands. The central point of the dorsal surface is generally a little 
depressed and devoid of pigment, and is but rarely extended lengthways or provided with 
a central pigment spot. There are also four pairs of pigment spots on, The margin corre- 
sponding to the suckers. The most frequent modification of this is shown in fig. 5, where 
it will be seen that there is an additional mass of pigment at each end of the median line, 
and that each of the marginal lines of pigment is divided into two parts. In the specimen 
displayed in fig. 9 the pigment is removed from the border of the body. On account 
of the lateral continuations of the marginal lines, this individual forms a transition to 
the varieties represented in figs. 6-11, which are characterised by the great quantity of 
pigment present, as well as by the unilateral or symmetrical anastomosis of the mar- 
ginal lines with each other and with the median line. Figs. 7, 8 are the extremes of 
these dark coloured forms ; fig. 8 shows a number of supernumerary spots, and a black 
border round the whole dorsal surface. There are also other varieties but slightly pig- 
mented (figs. 12-14), with an incomplete median line and without some of the marginal 
lines. One of the most aberrant modifications is shown in fig. 13 ; the light central 
point is wanting in this form, and the coloration is asymmetrical. 
The spirit specimens of Myzostoma horologium that I have in my possession vary in 
their ground-colour from white or sulphur-yellow to a dark brownish-yellow. Von 
