MEASUREMENT, ETC., OF UNIVALVES. 
35 
Plicate, or Lamellate, wlien the internal 
folds or teeth become rih-like in character, 
as in Piipd ftecale Drap. 
Fig. 87.— Example : Pit fa secale Drap. X 4, Mailing Hill, near Lewes, Sussex, collected 
by Rev. S. S. Pearce, M.A. 
Sept,4.te, when the interior of the whorls are 
contracted by projecting shelly processes, 
often leaving a tri-radiate opening for the 
molhisk, as in Segmentina nitida (Miill.). 
Fig. 
8.— Example : Segmentina nitida (Muller) X 3, Deal, Kent, collected by Mrs. 
Fitzgerald. 
Labiate, or Marginate, when callously thickened externally or 
internally at or near the margin, as in Helix nemomlis L., 
Helix hispida L., Pupa muacorum (L.), etc. 
Fig. 89. — An Externally Marginate Univalve. 
Pupa muscontm (L.) X 6, 
Stivington, Northampton, 
Collected by Mr. W. D. Crick, F.G.S. 
Fig. 90. — An Internally Marginate Univalve. 
Helix nemoralis L., 
Truro, Cornwall, 
Collected by Mr. J. H. James, A.R.I.C. 
The Length and Height of an ordinary spirally coiled LLiivalve 
shell are considered to be coincident and to be the distance from 
the base to the apex; some authors distinguish as simply the 
Length, or Height, the distance between the apex and the base of 
the umbilicus, and regard the distance from the lower part of the 
aperture to the apex of the shell, as the Total Length ; the Breadth 
is the distance through or across the most ventricose part of the shell, 
parallel with the plane of the aperture, this being the maximum 
diameter, the line through the whorls at right angles to tin’s, is 
the minimum diameter. The Patelliform Ancyli are usually con- 
sidered to have their Altitude or Height in the distance from the 
base to the apex or summit ; their Length in the distance from the 
anterior to the posterior margin of the aperture ; and Breadth in 
the distance from side to side. 
