1898.] NATURAL SCIENCES OF PHILADELPHIA. 287 



CHITONS COLLECTED BY DR. HAROLD HEATH AT PACIFIC GROVE, 

 NEAR MONTEREY, CALIFORNIA. 



BY H. A. PILSBRY. 



During the summer of 1897 Dr. Heath collected a series of inver- 

 tebrates and fishes for the Academy, including some twenty-four 

 species and varieties of Polyplacophora. As he has kindly engaged 

 to collect again during the present season, a full report on the 

 Chitons, with illustrations of new, unfigured and unusual forms may 

 be deferred until further specimens come to hand ; but it may be 

 well to enumerate the forms already seen, and describe two which 

 seem to be new. 



It is evident that the Mopalias require more study than has yet 

 been given them. At Pacific Grove, the typical muscosa, typical 

 lignosa and typical Hinclsii occur, without, so far as the series seen 

 shows, any specimens of intermediate character. The reference of 

 these to one species may, therefore, have been premature. A Mopalia 

 described below, differs from those hitherto known in the perfectly 

 regular form of the tail valve, which is like that of Ischnochiton, 

 thus breaking down, in large measure, the distinction between the 

 Ischnochitonidce and the Mopaliidce. This lawless species is new, 

 and I have given myself the pleasure of associating the name of my 

 friend Dr. Heath with it. 



The occurrence of two seven-valved adult monsters is also notable. 

 I shall return to these on a later occasion. 



LEPIDOPLETJRID^I. 



Lepidopleurus rugatus Cpr. 

 Lepidopleurus nexus Cpr. 



ISCHNOCHITONID^. 



Tonicella lineata Wood. 



Trachydermon (Cyanoplax) Raymondi Pils. 



A small form of the species, occurring in tide pools. 

 Trachydermon (Cyanoplax) Hartwegi Cpr. 

 Ischnochiton radians Cpr. 



This species is very similar to I. inter stinctus Gld., but the teeth 

 are longer and the slits decidedly deeper. 



