IREDALE : THE CHITONS OF THE KEEMADEC ISLANDS. 35 



ISCHNOCHITON KERMADECENSIS, n.Sp. PI. I, Fig. 3. 



Shell small, elongate, slightly elevated; valves faintly keeled; 

 girdle scaly. Coloration varied : commonly olivaceous of various 

 shades, sometimes splashed vpith lighter or darker; commonly 

 brownish, with a brick wash fading to dirty yellow, sometimes 

 splashed with lighter or darker markings, rarely with an uniform 

 dorsal broad light stripe ; frequently with lighter markings down the 

 back extending on to some valves so as to recall the var. picturatus 

 of /. smaragdinus ; no specimens with the markings of the var. decoratus 

 of /. crispus. Reeve, though similar markings occur in the Neozelanic 

 /. longicymha, Quoy & Gaimard, not Blainville = /. maorianus, 

 n.sp. Other colorations and variations occur more rarely. Anterior 

 valve faintly but closely radiately ribbed. Median valves with 

 the lateral areas small, but similarly sculptured ; pleural areas 

 finely quincuncially punctate. Posterior valve with the posterior 

 atea sculptured as the anterior valve, the anterior area as the pleural 

 areas of the median valves. Internal coloration generally greenish- 

 blue, but varying somewhat according to the external coloration. 

 Anterior valve has the smooth insertion-plate variously slit, apparently 

 the number of slits varying with age ; at least, I am unable to separate 

 the shells specifically, though dissections give the following results : 

 anterior 13 slits, posterior 12 slits; ant. 9, post. 8; ant. 12, post. 

 12; ant. 11, post. 10; ant. 12, post. 9; ant. 12, post. 11 slits. 

 The shells with the largest number of slits are the smallest, whilst the 

 shells with ih^ fewest slits are the largest. This is exactly the opposite 

 to my anticipations regarding insertion-plate slitting. I am still 

 engaged in the study of this variation in the slitting, and have made 

 many dissections with no definite result as yet. Median valves have 

 the sutural laminae short, broad, and placed far apart, the insertion- 

 plate with one slit, the posterior tooth quite unlike either that of 

 /. crispus (Reeve) or /. maorianus ( = /. longicymha, auct.). In some 

 cases it is longer than in others, but in all cases it is shorter than in 

 the former, though longer than in the latter. Posterior valve with 

 insertion-plate very short, and variously slit as above noted. Girdle 

 covered with very minute regiilaiiy striated scales. Juvenile shells 

 show a completely punctate surface, no radial ribbing being observed 

 either on the anterior and posterior valves, or on the lateral areas 

 of the median valves. As above noted, the slits in the anterior and 

 posterior insertion-plates seem to be more numerous in this stage and 

 decrease with age. Length of type 18, breadth 9 mm. 



Hah. — Sunday Island, Kermadec Group. 



Station. — On the underside of clean smooth stones below low tide 

 marks. " On smooth stones just below low- water lived species . . . 

 of Ischnochiton, of the crispus. Reeve, group." 



Remarks. — When Hedley & Hull described their Isvlmochiton 

 intermedins from Norfolk Island they observed: "This shell is 

 extremely common, and appears to occupy a position intermediate 

 between /. crisptis, Reeve, of Australia, and I. longicymha, Quoy, of 

 New Zealand. Compared with /. crispus, the novelty is more elevated, 



