GASTROPODA. 899 
Sulpingostoma.] 
on the dorsal part of the apertural expansion. The inner side of the aperture is 
always smooth. . 
Regarding the expanded aperture, we believe that it was developed only once 
during the life of the animal, and that it marks the fully matured condition. Two 
facts lead us to this opinion: first, the uniform size (in each species) of the speci- 
mens in which it is developed or preserved; and second, the thickness, as of age, to 
which the expanded rim may attain. As demonstrating the first we will give the 
results of measurements of two species. In ten ayerage specimens of 9. richmond- 
ensis the hight of the shell, excluding the apertural expansion, is 45 mm. in the 
smallest and only 50 mm. in the largest; in five specimens of S. buelli the same 
measurement varied between 35 and 37 mm. Herein lies the principal difference 
between Salpingostoma and Tremanotus, and it at the same time explains the 
development of a row of small openings in the latter instead of a single long slit. 
In Tremanotus, namely, the expanded aperture is a periodic development, a new 
one being formed at frequent intervals. There is, therefore, no narrow limit to the 
size of the specimen. The expansion is also always very thin, and the old ones were 
either broken away or reabsorbed, the latter being in our opinion more likely. As 
in Salpingostoma, the development of each expansion was preceded or accompanied 
by the anterior closing of the apertural slit, continued growth at last producing a 
row of openings instead of a continuous fissure. The number of these openings 
remaining uncovered varied probably according to their sizes and with the species. 
The only evidence on this point now available is furnished by casts of the interior. 
These seemed to show that they remained open for a distance equalling about a 
third of a volution. In this distance, which slightly exceeds the average length of 
the sht in Salpingostoma, different species of Tremanotus show from four to about 
ten openings. 
The surface markings of Tremanotus longitudinalis Lindstrom, the only species 
of the genus on which they have been observed in a thoroughly satisfactory manner, 
are on the whole more like those of Bucania than Salpingostoma, but as they are 
practically of the same type in all three genera, they are of but little assistance in 
referring a shell to its proper genus.* 
Finally, we wish to state emphatically our conviction that Bucania, Salpingos- 
toma and Tremanotus stand in close generic relationship to each other. The 
* Koken draws some fine distinctions between the different surface sculpturings of a number of European and one 
American species belonging in this connection, yet, if his observations on the others are not much nearer the truth than 
those which pertain to Tremanotus, they are certainly of little value. But we are perhaps more severe here than we intend, 
since in our opinion Dr, Koken has given usa most praiseworthy and valuable work. Because of the general minuteness 
and correctness of his observations, an error so palpable as the one he has fallen into with respect to Tremanotus is to be 
regretted more than condemned. Where he got the idea that the inner side of the aperture in Tremanotus is radially folded, 
and that “the folds are restricted to the inner side and in no wise dependent upon the outer side,” is beyond our compre- 
hension, It is simply not a fact, 
