148 EEV. T. R. E. STEBBING ON A NEW AUSTRALIAN 



genus, I shall endeavour to keep down the number of divisions in 

 this family by pointing out that what have been hitherto received 

 as two species oi Dynamene (or Cymodocea, Milne-Edwards), namely 

 rtij'bra and viridis, are in reality identical. If the colour of these 

 creatures is to be taken as a specific distinction, instead of two 

 species, we shall have to make a considerable group. Specimens 

 are exceedingly abundant at Torquay, and the coloration is very 

 variable. All are speckled, though to the unassisted eye many 

 appear to be plain green or red. The greens and reds vary from 

 very light to dark. Many of the green specimens have all the seg- 

 ments fringed with thin red lines. Some examples have a rich 

 brown or deep purple aspect, which under the microscope is found 

 to be produced by a close intermingling of small red and green 

 patches with crowded black specks over the whole surface. Very 

 frequently both on the red and green specimens there are two 

 conspicuous patches of light green — one on the body near the head, 

 the other on the tail. These look almost white against darker 

 shades of the same colour. Occasionally a thin line of lighter 

 colouring runs down the centre of the body, looking like a small 

 fragment of bleached coralline, such as the net often takes up in 

 sweeping for these creatures. Another variety has splashes of 

 dark brown or red on each side of the first body-segment and of 

 the tail, with smaller splashes on their segments. 



"What has been said of the colouring of D. rubra and D. viridis 

 will apply equally well to that of -D. Montagui. There are similar 

 variations also in Idotea tricuspidata, of which Sir J. Gr. Dalyell, 

 quoted by Spence Bate and Westwood, says, " their colour is 

 dingy or brownish yellow, with three or four white specks down 

 the centre of the back ; or it is altogether of variegated hues, and 

 some are mottled." Messrs. Bate and Westwood themselves say, 

 " this species varies greatly m its colour and markings ; generally 

 it is of a dirty greenish grey, but often has a pale longitudinal 

 line down the middle of the back or on each side of the body 

 whilst other specimens are marked, often irregularly, with large 

 pale yellow or orange-coloured patches on the body and tail. 

 According to our own experience, the colour of the animal is de- 

 pendent upon that of the weed on which it lives. Those that live 

 on the black fucus are generally very dark purple, while those 

 that we find on the green Alg(S are brightly verdant." The Tor- 

 quay specimens of I. tricuspidata, which are to be had in great 

 numbers, fully bear out these details of colour- variation ; and 



