r 
142 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
The varices or alternate swellings, characteristic of Tylostoma, are 
present, but not so conspicuous upon this example as they are upon 
some species of the genus, especially upon 7. mutabilis Gabb, another 
Mexican Cretaceous form; but they are quite as conspicuous as they 
‘are shown to be in the published figures of Sharpe’s typé species, T. tor- 
rubic. These varices or swellings are more apparent in our example 
by an apical than by a lateral view of it, but their presence is indicated 
in fig. 2 upon the ultimate and penultimate whorls. 
Although size cannot generally be relied upon as a specific character, 
the extraordinary dimensions of this shell separate it clearly from any 
other known form with which it might be otherwise in danger of being 
confounded. The only fossil species which resemble it, or even approx- 
imately approach it in size, are the Natica pedernalis and N. pra-grandis 
of Roemer, from the Cretaceous of Texas; but both these species evi- 
dently belong to a group that is now generally referred to Lunatia, or 
Huspira; and the largest known examples of either of these forms have 
scarcely more than half the dimensions of the example here described. 
DESCRIPTION OF TWO NEW SPECIES OF SEBASTICHTHYS (SEBA- 
STICHTHYWS ENTOWELAS AND SEBASTICHTHYVYS RHODOCHLO- 
RIS), FROM MONTEREY BAY, CALIFORNEA. 
By DAVID S. JORDAN and CHARLES H. GILBERT. 
Sebastichthys entomelas sp. nov. 
Allied to S. ovalis (Ayres). 
Body oblong, rather elongate, the back regularly but not strongly 
arched, contracted to a rather slender caudal peduncle. Head moder- 
ate, the profile less steep than in related species, but the tip of the 
snout blunter than in ovalis. Mouth small, the short maxillary extend- 
ing to below the middle of the eye. Lower jaw projecting, its tip enter- 
ing the profile, but considerably less protruding than in ovalis. Pal- 
atine teeth few. 
Preorbital very narrow, without spine. Eye rather large, about 4 in 
length of head, less than the interorbital space, which is strongly con- 
vex, especially in its middle part. 
Nasal spines minute. Preocular spine broad, triangular, rather prom- 
inent, more conspicuous than in melaneps. but much less so than in 
ovalis. Supraocular ridge little developed, its spine minute, sharp, con- 
cealed by the scales. Postocular spine present, minute, similarly con- 
cealed. No tympanic spine. Occipital ridges scarcely developed, 
concealed by the scales, without distinct spine at tip. In ovalis all 
these spines, though small, are distinet. In flavidus there is no trace of 
any spines on the cranium, and the ridges are little developed. 
Preopercular spines rather small, directed backwards, the two lower 
obsolete. Opercular spines small, two suprascapular spines. Scales on 
