POLYPLACOPHORA. 93 



(1). Species with naked girdle he calls Tonicia. 

 (2). Species with scaly girdle are called Lepidopleurus if the scales 

 are small, Gymnoplax if they are larger. 



(3). Species with spinose or hairy girdles are classed 



a. as Acanthoehites if tufts are present. 



b. as Chcetopleura if girdle has hairs. 



c. as Acanthopleura if girdle has spines. 



The names Schizochiton, Leptochiton, Onithochiton, etc. are used in 

 a variety of senses, or with no sense at all ; but in no case, so far as 

 I can learn, for the groups correctly so termed. Rochebrune's types 

 are in the Paris Museum. 



There are also included herein a few species carefully described 

 by well-known authors, but without reference to the internal char- 

 acters. These are mostly quite recognizable specifically, but they 

 require re-examination to ascertain their generic affinities. 



The species are grouped geographically. 



1. Northern Europe and N. Atlantic species. 



ONITOCHITON [sic] RHYGOPHILUM Rochebrune. Shell ovate, car- 

 inaied, ochraceous ; anterior valve smooth ; posterior part of the 

 posterior valve and lateral areas of intermediate valves very minutely 

 granulated ; central areas lacunose at the sides. Marginal ligament 

 somewhat wide, pale rufous. Length 17, breadth 10 mill. (Eochebr. 

 in Bull. Soc. Philom. de Paris, 1883-1884, p. 32). 



Coasts of Norway (Coll. Petit), rare Paris Museum. 



CHITON RARINOTA Jeffreys. Vol. XIV, PI. 4, fig. 86. 



Shell oblong-oval, arched, rather thin and glossy : plates broader 

 in the middle than at the sides; lateral areas indistinct. Sculpture 

 consisting of white tubercles, which are few in number and irre- 

 gularly scattered ; these are round in the middle of the shell, but 

 become more raised and oval at the sides ; under a microscope can 

 be detected numerous and close-set lines or striae, which are arranged 

 lengthwise ; colour whitish ; beaks none, except on the tail-plate, 

 where they are nearly circular: inside glossy. (Jeffr.} 



Length 2, breadth H mill. 



North Atlantic. 



C. rarinota JEFFR., Moll, of ' Lightning ' and ' Porcupine ' Expe- 

 ditions, in P. Z. S. 1882, p. 668, t. 50, f. 1. 



