32 TURBELLARIA OF PLYMOUTH SOUND. 
Seconp orn Mip-r1pan Zons.—This zone, daily covered by the tide, 
is characterised by the two species already mentioned, and also the 
following :—Aphanostoma diversicolor, Byrsophlebs graffi, Provortex 
balticus, Macrorhynchus naegelir, Plagiostoma vittatum, and Vorticeros 
auriculatum. Almost all these are provided with adhesive cells 
(Haftpapillen) at their posterior end, enabling them to retain their 
position during the wash of the tide. 
Tarp Zone.—Hxposed during spring-tides. Cylindrostoma quad- 
rioculatum, Convoluta flavibacillum, Hyporhynchus armatus, Acro- 
rhynchus caledonicus, Leptoplana tremellaris. This zone marks the 
lower limit of the Accela, and of the great majority of Rhabdoccela. 
Fourta Zone.—Depths up to 20 fathoms. Promesostoma solea, 
Provortex rubrobacillus, Cylindrostoma inerme, Plagiostoma girardt, 
species of Enterostoma, Stylostomum variabile, Oligocladus sanguino- 
lentus, Hurylepta cornuta. 
This sketch of the zones must be regarded as purely tentative, 
since my stay was not sufficiently prolonged to enable me to test 
these results. I was led to attempt such a classification from the 
striking absence of Accela and most Rhabdoccela below the Laminarian 
zone. On this subject there appears to be very little published work, 
and it would be a matter of some interest to ascertain the alterations 
in the vertical distribution of Turbellaria according to the difference 
of surroundings and tidal conditions at various parts of the coast. 
LocaL Disrripurion OF 'TURBELLARIA. 
Wembury Bay. 
My work in this bay has been restricted to an examination of the 
well-known collecting-ground exposed at low water below Wembury 
Church. So far as my experience goes, this appears to be (for 
Turbellaria) the richest locality in the neighbourhood of Plymouth. 
Nineteen species have occurred between tide-marks excluding four 
doubtfully new forms, which were either too rare or too immature for 
exact and thorough determination. 
It is not easy to define the characteristic Turbellarian features of 
Wembury Bay. ‘The abundance of Cylindrostoma quadrioculatum, 
O. inerme, Macrorhynchus naegelit, and Plagiostoma diovcum, together 
with five species of the Accela, and the apparent absence of Mono- 
tid, lend a provisionally distinctive aspect. 
The splendid tide-pools abounding in such alge as Cystoseira 
ericoides, Codium tomentosum, Bryopsis plumosa, are the best hunting- 
grounds. Among sand at the base of Corallina officinalis, curious 
