In one genus (Planorbis) the plasma of the blood is coloured red by haemoglobin, this being the only instance of the presence of this body in the blood of Glossophorous Mollusca, though it occurs in corpuscles in the blood of the bivalves Arca and Solen (Lankester).
In Planorbis, which is sinistral (as are a few other genera or exceptional varieties of various Anisopleurous Gastropods).
The nautiloid shell In Planorbis and in Auricula (Pulmonata, formed on the larva allied to Limnaeus) the olfactory organ is being cast, and a new on the left side and receives its nerve from shell of a different form the left visceral:ganglion.
Planorbis has the spire of the shell in one plane.
One can imagine the interest and astonishment with which the great Greek would have been filled had some unduly precocious disciple shown to him the red-blood-system of the marine terrestrial Annelids; the red blood of Planorbis, of Apus cancriformis, and of the Mediterranean razor shell, Solen legumen.
One species of Limnophilus uses small but entire leaves; another, the shells of the pondsnail Planorbis; another, pieces of stick arranged transversely with reference to the long axis of the tube.
In the same year, 1866, Franz Martin Hilgendorf (1839 - studied the shells of Planorbis from the Miocene lake basin underlying the present village of Steinheim in Wurttemberg, and introduced the method of examination of large numbers of individual specimens, a method which has become of prime importance in the science.