2/0 DR. P. P. CAKPENTER ON NEW SPECIES 



(^z=Le})i<7nplevrus, Add.,) known by the sharp incisor-teeth lying 

 within a projecting hp, there are three types of mantle-margin, 

 \vhi(;h mav be conveniently separated as subgenera, to aid in the 

 difficult task of describing and identifying species. The typical 

 forms, for which the uame Ischnoc/dfon should be retained, have the 

 scales somewhat chaffy, and very finely striated. /. maydalensia 

 and /. saiigidneus well represent the group. But another series have 

 the mantle-scales imbricate and strong, as in Chiton, Gray, (=.Lo- 

 jihyrus. Add.,) from which they cannot be distinguished without 

 dissection. For this Messrs. Adams's name Lepiduplcunis may be 

 retained in a restricted sense. It is uncertain what Kisso's original 

 genus was meant to include : his diagnosis applies to all Chitons 

 with distirict side-areas and scaly margins. 



A third group, sej)arated by Dr. Gray in his ' Guide,' p. 182, as 

 liaving the " mantle-scales minute, granular," has beeu nanred Tra- 

 chijdennon : it abounds in the Californian region. 



The specimens of L. adamsii were found among the duplicates 

 named Chiton disjjar by the Professor ; one was attached to Discina 

 cuminc/ii, 



Lepxdopleurus tenuisculptus. 



L. t. "L. adamsii" simili ; olivacea, colore pallida seu intensior^ 

 minute variegata ; iota sitperftcie minute granulosa ; orets 

 lateralibus vix dejinitis ; suturis plerumque albido muculatis ; 

 miicrone antico, satis conspicuo, parte postica concuva : intus, 

 lit in "L. adamsii "/on«oi'a. 



Variat : t. paUidore, adji/gum rvfo-tincta. 



= Chiton dispar, C. B. Ad. no. 373, i)ars. 



The outside of this shell so much resembles the young of Chi/or. 

 (Lophi/rus) stohesii, that specimens may have been distributed undei 

 that name. Very few individuals were found. 



ISCHNOCHITON ELENENSIS (diagU. aUCt.). 



Extus areis centralibus clathris parallelis circ. xx. decussatis , 

 ar. lat. costis ii., validioribus, tumidis, tuberculosis : intus 

 marginibus suturalibus posticis rejlexis, tubercxdatis, sinu ad 

 jugum parvo ; laminis insert ionis unijissis, ad laminas sufu- 

 rales anticas junctis, sinu lutissiino. Valva antica extus costis 

 xii., haud validis ; intus Jissuris x., dentibus acutis, subgrunda 

 parva, Valva postica niucrone subpostico, depresso ; parte 

 2)ostica exjyansa, concava, costis circ. xi. sububsaletis ; iidus 

 lamina insertionis circ. w.-Jissa, dentibus curtis, subgrunda 

 parva, intus callosa. 

 The central valves in this species are normal ; but the posterior 

 valve offers a transition towards Callochiton, the outside being con- 

 cave posteriorly, the iusertiou-teeth short and the eaves callous. 



ISCHNOCHITON (? var.) EXPRESSUS. 



I. t. "I. eleuensi" simili, sed carnea ; areis centr. clathris x., 



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