KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. N:o |G. 21 
farther towards the posterior end than it is in the West Indian ÅL. niger D'ORBIGNY, 
a difference between these very similar species pointed out by LYNGE 1909, who 
gives its distribution from the Red Sea and Zanzibar to China, Torres Strait, and 
Tahiti. HEDLEY (1916) records it from W. Australia. 
L. reticulatus DUNKER. 45 miles W. S. W., 48 feet (""/1), boring in a pearl 
mussle shell, 1 sp., 1. 20.5 mm. The present specimens agree very well with the figure 
given by DUNKER (MARTIN! & CHEMNITZ, Conch. Cab. 1882, Tab. 5 fig. 9, 10) and 
show the characteristic porous or reticulated crust covering the upper hinder part of 
the shell and projecting beyond its posterior end. DUNKER (1882) mentions the 
species from Java (?). 
FAM. ARCIDAE. 
Arca navicularis BRUGUIERE. 42 miles W. S. W., 70 feet ("”/s), 1 sp., 1. 23 
mm; 45 miles W. S. W., 60-70 feet, 5 sps, max. 1. 80, h. 34, thickness 37 mm; 
anovnersp., 1. 08, h. 32, br. 306 mm; 48 miles W. S. W., 140: feet, I sp., 1. 40 mm. 
The dimensions given illustrate the variation in form of the species in this locality: 
even in the position of the umbones and the sculpture of the area there is great 
variety. They agree in most points with A. navicularis from Japan (present in RB. M.!) 
but differ from it in more distant furrows. The species is distributed from Suez to 
N. Caledonia (LAMY 1907). 
A.imbricata BRUGUIERE, var. avellana LAMARCK (= Byssoarca maculata SoOWERBY, 
REEVE, Coneh. Icon, 2, Pl. XI, fig: 71, according to LAMY 1907). 45 miles W.S. W., 
60 feet ('/7), I sp., covered with spongiae, 1. 29 mm. — For the distribution (Indian 
Ocean to Japan) and synonyms see LYNGE 1909. 
A. complanata CHEMNITZ. 42 miles W. S. W., 70 feet ("”/s), I sp., 1. 41 mm; 
45 miles W. S. W., 66 feet ("””/s), 2 sps, I. 50 mm; 48 feet (”/r), 2 sps, max. 1. 27 mm. 
The sculpture of these specimens most closely approaches that of the form Arca 
velata SOWERBY, but the position of the umbones resembles that of specimens of ÅA. 
decussata, from Eimeo for example (R. M.). The present form differs from both in 
having a wing in the posterio-superior corner; in this characteristic it agrees with 
the ffgure of ÅA. decussata given by REEVE (Conch. Icon. 2, 1844, Pl. XII, fig. 81). 
LYNGE (1909) comprises both ÅA. velata and ÅA. decussata in A. complanata. The 
species has a wide distribution from the Red Sea to Japan, New Zealand, Society 
and Galapagos Islands (LYNGE 1909). 
A. plicata CHEMSiTzZ (= divaricata SowEerBY). 45 miles W.S. W., 66—70 feet 
("”/7), 2 sps., max. 1. 18 mm. The sculpture completely agrees with figs. 108 and 
112 in REEvE (Conch. Icon. 2, 1884), but the shape is variable; the large specimen 
! Swedish State Museum of Natural History (»Riksmuseum >). 
