A. EL Verritt— Catalogue of Marine Molluseu. 157 
The uncini are relatively large and strong, being four or five times 
larger than in P. Agassizii. They form two, regular, convergent 
rows. he shaft is obloug-linear, flattened and twisted near the tip, 
and strongly barbed on both edges, the barbs unequal; base amber- 
colored, short, flattened transversely to the shaft, with the edge some- 
what recurved, and with an oblique, short, hood-shaped appendage 
on one side. Length of uncini, 0426"; of shaft, 033"; breadth 
of shaft, °0027"™; of base, 0087". 
A living specimen was taken in 1880, at station 895, in 238 tath- 
oms. Single specimens were also dredged in 1881, off Martha’s 
Vineyard, at stations 938 and 947, in 310 and 312 fathoms. The 
last was living, but not quite mature. The animal in both living 
specimens was so far retracted that it could be extracted only by the 
use of potash, so that it could not be described. 
Bela (Leach); H. & A. Adams; G. O. Sars, &e. 
Pleurotoma (pars) Jeffreys, and many earlier authors. 
The species of this genus are numerous on our coast, but their 
identification has been very difficult, mainly owing to the very poor 
and insufficient descriptions that have been given by many writers. 
Mdller’s Greenland species, especially, are so brietly and poorly de- 
scribed that it is impossible to identify most of them, without refer- 
ence to his original specimens.* 
Fortunately, the recent admirable work of Professor G. O. Sars 
contains excellent illustrations of the shells and odontophores of most 
of the northern European species, many of which are identical with 
ourown. His workt is indispensable for the proper study of this group. 
Aside from the imperfections of the published figures and descriptions, 
the shells are themselves variable and difficult to determine satis- 
factorily, especially when one has large series of specimens from nu- 
merous localities. Most of the species change greatly, both in form 
and sculpture, during growth, and some examples often retain juve- 
nile characters later than others of the same species. In Binney’s 
edition of Gould’s Invertebrata of Massachusetts there are included 
seven northern species of ela. Of these, the figures are mostly 
inadequate, and some are entirely erroneous. Fig. 620, given for Bb. 
* Moller’s collection is now in the Museum of Copenhagen. Several of his species 
of Bela were previously and better described by Couthouy, Gould, and others, in this 
country. 
+ Mollusca Regionis Arcticee Norvegise, Christiania, 1878. 
