ORTMANN: FAMILIES AND GENERA OF NAJADES. B35) 
the outer walls of the marsupium, around the edges of the placenta, 
which are central. Glochidia of peculiar shape, small, much longer 
than high. 
Type D. dromas (Lea). 
This is a highly interesting genus, = several quite unique features 
(general shape of marsupium, arrangement of glochidia and placente, 
shape of glochidia), bu1 there is no question that it belongs to the more 
primitive types of the Lampsiline. In young specimens, where the 
marsupium is not folded, the marsupium resembles somewhat that of 
Obovaria, but without being so swollen. The general shape of the 
shell, as well as the shape of the glochidia can only be compared with 
that of Cyprogenia. I do not think that the folded marsupium in- 
dicates closer relationship to Ptychobranchus, since here the folds are 
of a different character. In the absence of special structures on the 
edge of the mantle, this genus shows only a low stage of specialization, 
without pointing to any particular affinity with other forms. 
Dromus dromas (Lea). 
I am indebted to B. Walker for seven complete specimens, and the 
soft parts of nine others, all from the Cumberland River, in Pulaski, 
Russell, Wayne, and Cumberland Cos., Kentucky. One of the soft 
parts was a male, the others were all gravid females with glochidia. 
They all were collected late in 
the season of 1910, so that the 
beginning of the breeding season 
is in autumn. 
The description of the marsu- 
pium given by Simpson (1900), 
p. 615) is entirely inadequate 
and directly misleading, and in 
one particular (‘‘bases of the 
ovisacs slightly rounded’’) un- 
intelligible HRKe “antes Dromus dromas (Lea). 
Awal o araved oft Gravid female, young (shell 41 mm. 
Be OPES HP < om long), from Cumberland River, Albany 
the supra-anal by a very short Landing, Cumberland Co., Ky. (Carn. 
and deciduous mantle-connec-  Mus., No. 61, 4,970.) 
tion: only in two young and one 
older specimen was the latter preserved; but the others had been 
rather roughly handled and the posterior region of the mantle was 
