MOLLUSCA FROM JUAN FERNANDEZ AND EASTER ISLAND 22 1 



I. Cephalopoda. 



Octopus tuberculatus Blainville. — Masatierra, lo — 35 m, sand and Coral- 

 lina, 2 sps., max. 1. 30 mm; 30—40 m, 4 sps., max. 1. 27 mm ('V* I9'7)- 



2. Lamellibranchia. 



*Lima angulata Sowerby. — Masatierra, 30—40 m, sand and Corallina, 

 I sp., 1. 12 mm C/i), and i sp., 1. 9,5 mm (^V* 1917)- 



Modiolaria (Gregariella) opifex Philippi. — Masatierra, 30—45 m, Coral- 

 lina bottom, 6 sps., max. 1. 10 mm (^^/a 1917). For the distribution of this 

 species see Lynge 1909.^ 



Modiola plumescens Dunker. — Masatierra, 30—45 m, Corallina bottom, 

 I sp., 1. 12 mm (^Va). Distribution from the Samoa Isl. and Australia to Java 

 and Siam (Lynge 1909 s Odhner 1917^). 



Avicula [Stempellia n. subg.) aequivalvis n. sp. PI. 8, figs. 3, 4. — Shell 

 rather thick, squarely rounded, with a pointed apex at the junction of the 

 straight dorsal and the anterior margin. No auricles; posterior margin directly 

 descending from the dorsal one, and slightly convex; inferior one well rounded, 

 passing into the anterior, which is faintly S-curved by the presence of a byssal 

 sinus close beneath the apex. Surface shining, sculptured by about 6 distant, 

 almost angular, ridges radiating from the umbones to the inferior margin. Colour 

 pale brownish with two dark-brown cloudy stripes, one, at the dorso-posterior 

 corner, the other, on the infero-posterior part of the shell. Interior white, not 

 nacreous. Margins smooth, bordered with a faint callous simple pallial line all 

 round near the edge, thickening inside the dorsal margin to a ridge bounding 

 the umbonal cavity, and dilating to a septum in front beneath the apex. Dimen- 

 sions of the shell: length 6, height 4,4, thickness 2,8 mm. 



Only one empty shell, the left valve of which was somewhat injured, was 

 collected at Masatierra, 20 — 35 m, sand and Corallina (^V*)- 



The nearest ally of this characteristic species is evidently A. magellanica 

 Stempell 1899^ from Magellan Strait. These both species have many peculia- 

 rities in common, by which they differ from the true Aviculae, thus f. i. the 

 absence of the auricles and of the nacreous lining of the shells; the presence of 

 the radiating sculpture, and above all the aequivalvity of the shell. These 

 characters justify the creation of a new subgenus for both species, to which I 

 propose to apply Stempell's name as a tribute of estimation of his contribu- 

 tion to our knowledge of the Fauna Chilensis. 



^ The Danish Expedition to Siam. IV. Marine Lamellibranchiata. Mem. Acad. Roy. des 

 Sci. et des Lettres de Danemark, Copenhague, 7n»e ser., t. V, no 3. 



' Res. of Dr. E. Mjoberg's Swed. Sci. Exp. to Australia. XVII Mollusca. K. Sv. Vet.- 

 Akad. Handl, Bd 52, No. 16. Stockholm. 



' Die Muscheln der Sammlung Plate. »Fauna Chilensis» II. (Zool. Jahrb. Suppl.-Bd. V.) 



