80 
MOLLUSCA. 
ORDER IX. 
CYCLOBRANCHIATA *. 
The branchise of the Cyclobranchiata resemble small lamellm, or 
little pyramids forming a cordon more or less complete under the 
borders of the mantle, very nearly as in the Inferobranchiata, from 
which they are distinguished by the nature of their hermaphroditism ; 
for, like the preceding genus, they have no copulating organ, but fe- 
cundate themselves. Their heart does not embrace the rectum, but 
varies as to situation. But two genera of this order are known, in 
both of which the shell never approaches in the least to the turbi- 
nated form. 
Patella, Lhi . 
The entire body covered with a shell, formed of a single piece, in the 
form of a broad-based cone ; a cordon of little branchial lamellse 
under the margin of the mantle; the anus and genital orifices some- 
what to the right and a])Ove the head, which is furnished with a 
thick and short snout, and two pointed tentacula, on the external base 
of Vidiich are the eyes ; the mouth is fleshy, and containing a spiny 
tongue, which inclines backwards, and is reflected deeply in the in- 
terior of the bodJ^ The stomach is membranous, and the intestine 
long, thin, and greatly flexed ; the heart is forwards, above the neck, 
and a little to the left f . 
Some species abound on the coast of France. 
Chiton, Lin . 
A range of testaceous and symmetrical scales along the back of the 
mantle, but not occupying its whole breadth ; edges of the mantle 
* M. de BlainviUe, who calls the order in which he places Dui-is Cyclobran- 
cniATA, makes an order of the Patellae, and of the three preceding genera, which 
he names Cervicobranchiata, which he divides into thei?rfj/era and the itranc/ii- 
fera. The Refifera are the Patella, because he supposes that they respire through 
the medium of a network in the cavity which is over their head. I have vainly 
sought for it, however, nor could I diseover there any other organ of respiration than 
the cordon of lamellae which extends round the under part of the margin of the 
mantle. See Anat. of the Patel'aiii my Mem. on the Mollusca. 
•h I separate from the Patkll.® and arrange among the Trochoida, all the 
animals comprised in the genera, Crepidula, Navicella, Calyptr.ea of M. de 
Lamarck, to which I add the Capuei ; and his genera Fissurella, Emarginula, 
and Parmophora, or Patella ambigua, Chemn., XI, 197, 1918, I place among the 
ScDTiBRANCHiATA. The UMBRELLA, Scutus, Moutf., — Patella umbrella, Martini 
II, vi, 18, is one of the Tectibranchiata. The Pat. anomala, Miill., belongs to 
the Brachiopoda and is my genus Orbiculus. The other species quoted by Gm. 
remain in the genus Patella. 
