Counting The Number of Whorls
To count exactly the number of whorls in gastropods a straight line is drawn to separate the semi-circular nucleus (protoconch (1 - see image) from the younger part of the shell. An arrow placed at a 90° angle on this line, following the course of the whorl, reaches the end of the first whorl where it is parallel to its starting position. From that point all whorls are counted towards the margin of the shell, estimating the ultimate whorl with an accuracy of a quarter whorl.
Other authors (Ehrmann 1933; Richter & Seapy 1999) applied a slightly different measuring method, resulting in whorl numbers being a quarter higher.
Read more about this topic: Whorl (mollusc)
Famous quotes containing the words counting the, counting and/or number:
“Nights, I squat in the cornucopia
Of your left ear, out of the wind,
Counting the red stars and those of plum-color.
The sun rises under the pillar of your tongue.”
—Sylvia Plath (1932–1963)
“But counting up to two
Is harder to do....”
—Philip Larkin (1922–1986)
“The Oregon [matter] and the annexation of Texas are now all- important to the security and future peace and prosperity of our union, and I hope there are a sufficient number of pure American democrats to carry into effect the annexation of Texas and [extension of] our laws over Oregon. No temporizing policy or all is lost.”
—Andrew Jackson (1767–1845)