FAMILY SPHMROMIDA. 81 
for solving the problem ; I suppose, however, that the same 
structure is found in Chitinopsis (Whitelegge) and in 
Cassidina typa (M.-Edw.), and the latter form being com- 
paratively large, a study of a rich material of females in 
various stages will be the best material for a future study of 
the anomalous and interesting mode of construction of the 
incubatory chamber in the section Cassidinini. 
The perusal of the preceding pages will convey an idea of 
the astonishing variation met with not only in the family 
Spharomide but even in the sub-family Spheromine as to the 
structure of the chamber for the development of the brood. 
Let us give a brief abstract. In some genera, as Limnoria, 
Dynamene, and Vireia, the room is formed only by the 
usual lamelle, which are very or exceedingly large; in 
Plakarthrium the same arrangement is found, but the 
lamellz are of moderate size. In Spheroma and Cymodoce 
the brood is developed in four or five pairs of pouches pro- 
ceeding into the animal and opening with rather long trans- 
verse slits at some distance from the mesial line, while the 
marsupial lamelle overlap each other; in Bregmocere la 
we find the same arrangement, but the openings of the pouches 
are minute; in Hxospheroma, Isocladus, and Zuzara the 
marsupial lamellze are small and far from reaching each other 
at the mesial line, while the apertures of the inner pouches 
are small or minute, situated near the base of the lamelle, or 
even impossible to discover. In Paraspheroma two pairs 
of apertures of internal pouches are longitudinal slits at the 
base of the lamellae. In Cymodocella and Ancinella the 
major posterior part of the incubatory chamber is formed by 
a single external exceedingly large pouch with a very broad 
aperture directed forwards, while the anterior part of the 
chamber is formed by the marsupial lamelle. In Cassi- 
dinidea and Leptosphzroma the marsupial lamelle are 
wanting and the chamber is formed by a posterior and an 
anterior external pouch united with each other. 
But the structure is still more complicated and varied. In 
the following chapter it is shown that im a little more than 
vot. 49, parT 1.—NEW SERIES. 6 
