LOTTIA. 



externally; in Lo^/ia on the contrary the branchiae form 

 but a single row which is contained in a cavity over the 

 neck of the animal, a part being perhaps occasionally 

 protruded ; and if sometimes entirely visible, they are then 

 seen in ferm of a plumose appendage passing out of the 

 cavity on the left side of the head. Easy however as it is 

 to distinguish Lottia from Patella by the situation of the 

 branchiae in the animal, it is extremely difficult to distin- 

 guish it by the shell alone ; we will endeavour to point 

 out its most prominent characters. 



In general form as we have already stated it is very 

 much like Patella, though flatter and not so conical, its 

 vertex which as in that Genus is anterior, is more nearly 

 approximated to the anterior margin than it usually is in 

 Patella; in some instances it is very nearly marginal. 

 The edge of the shell varies according to the nature of 

 the outer surface, if that be smooth the edge is sharp and 

 free from notches or any other irregularity; if on the 

 contrary that be grooved or striated the edge is more or 

 less deeply or broadly notched. In this circumstance it 

 does not differ from F^atella in the least. The great 

 difference in the branchia of the animal would have led 

 us to suppose that some important difference might have 

 been found in the muscular impressions, because as a 

 general observation, the nioilusca whose branchia are 

 symmetrical produce in most respects symmetrical shells, 

 and the muscular impressions also are symmetrical, and 

 this is the case in Patella. The dissimilarity in the two 

 sides of the muscular impression of Lottia is however, very 

 slight, it being rather wider on the right side near the 

 head than on the left. Mr. Gray thinks he has observed 

 that in the Lottiae the internal central disk is generally 

 of a dark or varied colour. 



As far as we know at present the species of this Genus 

 are only found on the shores of the South American 

 Continent and Islands, where however it is probable there 

 are a great number; specimens of the same species vary 

 greatly in form. 



Fig. 1. Lottia gigantea, Gray. 



2. testudinaria. Patella testudinaria, Auctorum. 



3. radians, nobis. 



4. — — — Antillarura, nobis. 



