KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. wn:o I6. 21 
farther towards the posterior end than it is in the West Indian L. niger D’ORBIGNY, 
a difference between these very similar species pointed out by Lynar 1909, who 
gives its distribution from the Red Sea and Zanzibar to China, Torres Strait, and 
Tahiti. Hepiey (1916) records it from W. Australia. 
L. reticulatus Dunker. 45 miles W. S. W., 48 feet ('%/7), boring in a pearl 
mussle shell, 1 sp., 1. 20.5 mm. The present specimens agree very well with the figure 
given by Dunker (Martini & CuEmNiItTz, 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. DuNkeER (1882) mentions the 
species from Java (?). 
FAM. ARCIDAE. 
Arca navicularis Brucurbre. 42 miles W. 8. W., 70 feet (°/s), 1 sp., 1. 23 
mm; 45 miles W. 8S. W., 60—70 feet, 5 sps, max. 1. 80, h. 34, thickness 37 mm; 
another sp., 1. 68, h. 35, br. 36 mm; 48 miles W. 8. W., 140 feet, 1 sp., lL 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 R. M.’) 
but differ from it in more distant furrows. The species is distributed from Suez to 
N. Caledonia (Lamy 1907). 
A. imbricata Bruauiiree, var. avellana LaMArcK (= Byssoarca maculata SOwERBY, 
Reeve Conch. Icon. 2, Pl. XI, fig. 71, according to Lamy 1907). 45 miles W. 8. W., 
60 feet (°/7), 1 sp., covered with spongiae, 1. 29 mm. — For the distribution (Indian 
Ocean to Japan) and synonyms see LyncGe 1909. 
A. complanata Cuemnirz. 42 miles W. S. W., 70 feet (°°/s5), 1 sp., 1. 41 mm; 
45 miles W. 8. W., 66 feet (7°/s), 2 sps, 1. 50 mm; 48 feet (*/7), 2 sps, max. |. 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 A. 
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 figure of A. decussata given by ReEveE (Conch. Icon. 2, 1844, Pl. XII, fig. 81). 
Lynce (1909) comprises both A. velata and A. 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 Cunmnitz (= divaricata Sownrspy). 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»). 
