( ill TOPLS1 i: \. -7 



This very peculiar shell rescmUes .Mopalia Mainvillei in mantle 

 and inner.); and Nuttallina in tin- ln.L r , Mnooth plate.-, -eparaN d l.y 

 a d.-ep, not laminated sinn<. Tin- side slils how, and 



deep instead of duplicate and angular, as in thai 

 rior plates are not tin-own forward nor waved as in Mopalia. I^av- 

 \i\^ out of view the anterior prolongation of the mantle, which \ a 

 variable character even anioni: Mopalia, it may be regarded as a 

 partially covered Tonicella. The slits are abnormally few, as in 

 Leptoplax. But for the characters of the tail plate I should have 

 considered it intermediate between Mopalia and Katherina. (< 



Genus VII. CH^TOPLEURA Shuttleworth, l*f>3. 



Chcctopleura SHUTTLW., Diagn. neuer Moll. no. 4, iiber den Ban 

 der Chitoniden, etc., in Bern. Mittheil. p. 66, June, 18~>3 (~ Acan- 

 thopleuraGray, ex parte). Choetopleura CPR. MS. and DALL, 1'roc. 

 U. S. Nat. Mus. 1878, p. 329, type C. peruviana Lam. Acantko- 

 pleura, GRAY, Guide Moll. B. M. p. 183. 



Valves as in Ischnochiton ; eaves solid ; girdle leathery, more or 

 less hairy ; gills extending almost or entirely to the front end of the 

 foot. 



The present group seems to me to stand naturally on the confines 

 of the Ischnochitonoid series, having decided relations to the true 

 Chitons and especially to Tonicia. 



Carpenter made a subgenus, Maugerella, under Chcetoplcura, for 

 a Radsioid Californian form, which I have excluded from the genus, 

 as its affinities are with the Radsioid Ischnochitons. The following 

 able discussion of this genus is from Carpenter's MS. : 



Shuttleworth, in distinguishing this genus from Acanthopleura by 

 the mantle characters only, does not seem to have observed the co- 

 ordinate differences in the hind valve and the insertion plates. 

 Messrs Adams united to this genus Eudoxochiton and Craspedo- 

 chiton which do not belong to the same section. Gray, in his 

 " Guide," p. 183, ignores the genera of Shuttleworth, but preserves 

 the distinction between Chsetopleura and Acanthopleura. Most 

 unfortunately, however, he chooses to keep the name Acanthopleura 

 for Chsetopleura of Shuttleworth and Add., and makes a fresh name 

 Maugeria for the restricted Acanthopleura of Shuttleworth and 

 Add. Even if Shuttleworth had been unwise in his mode of 

 division, he would have been entitled to precedence ; but fortunately 

 he kept Acanthopleura for the first section of Guilding's group, 



