90 HYALINIA RADIATULA. 
The TEETH of H. hammonis are described by Dr. Lehmann as consisting of 
eighty transverse rows, each composed of a mid-area of seven to nine teeth, and a 
marginal area on each side with about twenty-four aculeate teeth. The mid-tooth 
is tricuspid, and larger than the adjacent laterals, and which are also described as 
tricuspid, while the marginals are long and thorn-like upon an acutely triangular 
base. The formula is given by Schepmann as 22+$+34+3+ 72% 
m q = 4 13 18 
ig yt mn An a ra VA ae 
Fic. 134.—Representative denticles from a transverse row of the teeth of Wyadinia hamimonis from 
Rhoon, Holland x 600 (after Schepmann). 
Habits and Habitat.—Z. radiutula and its allied forms or varieties 
are alike in being strictly geophilous, and in preferring a moist habitat, 
whether it be amongst the moss and grass in damp pastures or beneath 
stones and decaying leaves in woods, ditches, and damp places generally, 
though it is occasionally recorded as found in dry situations. 
During the day they ensconce themselves beneath the lowest layer of 
moist decaying leaves, usually indeed on the wet ground or attached to 
the underside of the lowermost leaves. 
In winter they retire deeply within the dense tufts of grass on the outer 
edge of the boggy land, secreting a very thin and vitreous epiphragm, but 
on favourable occasions becoming active, even as early as January. 
It is a very bold and active species, continually exserting and retracting 
its tentacles and often crawling actively about with tentacles quite with- 
drawn within the body. 
In its varietal form, petronella, it ascends to considerable heights, and 
in Piedmont, according to Signor Pollonera, inhabits the mountains from 
5,000 to over 9,000 feet altitude, being replaced on the lower slopes by 
the type form, which does not ascend beyond 5,000 feet ; it also becomes 
more generally prevalent towards the north and towards the confines of 
its distributional area, extending in the Scandinavian peninsula beyond 
the oak region, up to that of the willows and pines and far into the 
region of the birch. 
‘he HEART is, as in other species, stimulated to increased activity by 
warmth and retarded by cold. ‘The pulsations of a specimen at 27° Fahr. 
were observed to be barely nine per minute; at 54° they had risen to 
forty-four ; at 62° the contractions were fifty-two per minute; while at 
65° they attained a rapidity of fifty-five in the same space of time. 
Geological Distribution.—Hyalinia radiatula, though so ancient 
and widely distributed, has not as yet been found beneath the Lower 
Pliocene deposits on the continent, nor lower than the Pleistocene in this 
country and America. 
Lower Priocene.—Recorded by M. Locard from Hauterive in the 
department of the Dréme, France. 
PierstoceNe.——In South Wilts., it is reported by Mr. Kennard from 
river deposits at Fisherton, near Salisbury. 
In East Kent, it is recorded from the freshwater marls of Maidstone 
and Charing by Prof. Morris. In West Kent, it is listed by Mr. Abbott 
amongst the species found in the Ightham fissure near Wrotham, recorded 
for the Pleistocene beds of Crayford and Erith by Mr. A. Tylor, by Mr. 
B. B. Woodward for Stoneham’s Pit, Crayford, and by Mr. Kennard from 
the sandy-gravel river deposit so marvellously rich in mollusca at Swanscomb. 
