2i6 The Irish Naturalist. Kovember, 
IRISH SOCIETIES. 
ROYAL ZOOLOGICAL SOCIETY. 
Recent gifts include a Suricate from Mrs. Rowan, Undulated Grass 
Parakeets and Cockateels from Mr. A. Goodbody, two Peahens from 
Mr. J. Collin, and a Great Northern Diver from Mr. J. Keith. A Striped 
Hyaena, a. Hooded Crow, a pair of Peafowl, a Yokohama Cock, a pair of 
Hen Harriers, and a Merlin have been received on deposit. 
The Society has sustained a great loss by the death of Patrick Supple 
who has been over fifty years keeper in the Gardens, and for most of that 
time has been in charge of the Monkey House. 
DUBLIN MICEOSCOPICAL CLUB. 
October 8. — The Club met at Leinster House. J. H. Woodworth 
(President) in the Chair. 
Prof. G. H. Carpenter showed a new species of Petrobius from the 
shore of Portrane, Co. Dublin, with drawings showing the structural details 
by which it may be distinguished from the common P. mavitUnus Leach. 
It will shortly be described and figured in the Ivish isaturaUst. He also 
demonstrated the presence of a few minute but distinct teeth at the apex 
of the mandible in the final cuticle as formed beneath that of the penulti- 
mate instar before the last moult. It .seems that these teeth arc 
worn down immediately after the moult, so that the untoothcd mandibular 
apex becomes a generic character for Petrobius. 
N. CoLGAN exhibited a series of slides illustrating changes effected 
during the process of growth in the form of the radula in certain species 
of opisthobranch mollusca. Amongst the species selected as affording 
instances of these changes were Aplysia punctata, Tritonia pleheia and 
Deyidronotiis arboresccns, in all of which the broad lingual ribbon is com- 
posed of several transverse rows of teeth, each row having a large central 
tooth flanked on either side b\^ numerous smaller lateral teeth or uncini. 
The radula or lingual ribbon of a 6 mm. specimen of Tritonia pleheia was 
shown to have 26 rows, of which the widest had 50 laterals on either side, 
while the radula of a 20 mm. specimen of the same species had 38 
rows with 70 laterals. In Apl3'sia the number of rows and of laterals 
in the widest row was found to vary from 21 and 10 in a specimen 12mm. 
long to 46 and 17 in a specimen 175mm. long. These numerical varia- 
tions were found to be accompanied by variations in the form of the teeth 
in the direction of blunting or simphfication of outline with increasing 
age and size. Thus in Dendronotus arboresceiis, the tips of the uncini, 
sharply denticulate in the younger and smaller individuals, became quite 
smooth in the largest specimen. In Aplysia the growth changes were 
most conspicuous in the central teeth whose outline became remarkably 
altered by unequal development of the parts. Examination of a large 
