MOLLUSCA FROM JUAN FERNANDEZ AND EASTER ISLAND 221 
1. Cephalopoda. 
Octopus tuberculatus Blainville. — Masatierra, 10O—35 m, sand and Coral- 
lina, 2 sps., max. 1]. 30 mm; 30—40 m, 4 sps., max. I. 27 mm ('"/4 1917). 
2. Lamellibranchia. 
*Lima angulata Sowerby. — Masatierra, 30—40 m, sand and Corallina, 
I sp., |. 12 mm ('/4), and 1 sp., l. g,5 mm (11/4 1917). 
Modiolaria (Gregarze//la) opifex Philippi. — Masatierra, 30—45 m, Coral- 
lina bottom, 6 sps., max. l. 10 mm (?*/3 Ig17). For the distribution of this 
species see LYNGE 1909.' 
Modiola plumescens Dunker. — Masatierra, 30—45 m, Corallina bottom, 
I sp., 1. 12 mm (78/3). Distribution from the Samoa Isl. and Australia to Java 
and Siam (LYNGE 1909’, 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 (**/s). 
The nearest ally of this characteristic species is evidently A. magellanica 
Stempell 1899? from Magellan Strait. These both species have many peculia- 
tities 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. 
1 The Danish Expedition to Siam. IV. Marine Lamellibranchiata. Mem. Acad. Roy. des 
Sci. et des Lettres de Danemark, Copenhague, 7m™e sér., t. V, n° 3. 
? Res. of Dr. E. MjOserc’s Swed. Sci. Exp. to Australia. XVII Mollusca. K. Sy. Vet.- 
Akad. Handl., Bd 52, No. 16. Stockholm. 
8 Die Muscheln der Sammlung Plate. »Fauna Chilensis» I. (Zool. Jahrb. Suppl.-Bd. V.) 
