418 
MOLLUSCS. 
attach themselves to other shells by their right valve, the left being ornamented 
with radiating ridges. Among the other families, Anatina, Thracia, and Pltola- 
domya are interesting genera, the last on account of its rarity in the living condition, 
and its numerous representatives in bygone ages. Brechites, or Aspergillum , is 
remarkable, as it is only in the earliest stages of existence that it presents the 
appearance of a normal bivalve. It subsequently forms an elongate tube, open at 
one end and 
closed at the 
other by a 
frilled disc full 
of holes, like 
the rose of a 
watering - pot; 
e m b r y o n i c 
valves being 
embedded in 
the surface near the rose. The illustration shows the contracted animal extracted 
from the shell, (e) indicating the siphonal openings, (c) the mantle aperture, ( b ) the 
anterior side, (a) the mantle, ( d ) foot opening. 
Brechites vaginiferus. 
A, Animal contracted, withdrawn from shell; B, Anterior end of the shell. 
Order Septibranchiata. 
The members of this group are readily distinguished by the circumstance that 
the gills are transformed into a muscular septum, extending from the anterior 
adductor to the separation of the two siphons, and surrounding the foot, with 
which it is continuous. This septum presents symmetrical orifices. The siphons 
are sometimes short, or more or less produced. There are two adductors, 
and the mantle - edges are united at three points. There are two families, 
namely, the Poromyidce and Cuspidariidce. Of the former, Poromya has the 
siphons short, unequal, separate, and surrounded by a tentacular fringe; each 
half of the septum having several groups of lamellae, separated by orifices; the 
foot being slender, long, and the palpi larger. The shells are often minutely 
granular and somewhat pearly within. The species are small, few in number, 
and mostly from very deep water. Silenia is a deep-water form, dredged in 1950 
fathoms, about eleven hundred miles south-west of Australia, and also in the South 
Atlantic at the enormous depth of 2650 fathoms. The Cuspidariidce is a more 
extensive family, and although the species are nearly all small, some are elegant in 
form, and prettily sculptured. The shells have been classified by characters derived 
from modifications of the hinge, and the surface ornamentation. The siphons are 
longer than in the Poromyidce and united with tentacular fringes at the ends; the 
foot is moderately long and pointed, the labial palpi are rudimentary or wanting, 
and the branchial septum is pierced with isolated symmetrical orifices. The shells 
are mostly transversely ovate, and produced posteriorly into a more or less elongate 
rostrum. They are found in all seas, in depths ranging from a few fathoms to over 
three miles. 
EDGAR A. SMITH. 
