MOLLUSCA. 



ORDER IX. 



CYCLOBRANCHIATA *. 



The branchiae of the Cyclobranchiata resemble small lamellae, 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, Lin. 



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 lamellae 

 under the margin of the mantle; the anus and genital orifices some- 

 what to the right and above the head, which is furnished with a 

 thick and short snout, and two pointed tentacula, on the external base 

 of which 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 body. 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 Bliua\-ille, who calls the order in which he places Doris Cyclobran- 

 chiata, makes an order of the Patellfe, and of the three preceding genera, which 

 he names Cervicobranchiata, which he divides into ih^Reti/era and the Branchi- 

 fera. The Refifera are the PateUfe, because he supposes that they respire through 

 the medium of a network in the cavity which is over their head. I have v.iiniy 

 sought for it, however, nor could I discover 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 Patella iu my Mt^-m. on the MoUusca. 



•f- I separate from the Patkll^e 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 C.\pui,i ; and his genera Fissurella, Emarginula, 

 and Parmophora, or Patella amhiguu, Chemn., XI, 197, 1918, I place among the 

 ScuTiBRANCHiATA. The UMBRELLA, Scufus, Montf., — 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. 



