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 T. niutahllis Gabb, another 

 Mexican Cretaceous form; but they are quite as conspicuous as they 

 are shown to be in the i)ublished figures of Sharpe's type species, T. tor- 

 rwbice. These varices or swellings are more apparent in our example 

 by an apical than by a lateral view of it, but their x^resence 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 JSfatica pedernalis and ¥, jprw-graiidis 

 of Eoemer, from the Cretaceous of Texas; but both these species evi- 

 dently belong to a group that is now generally referred to Lunatia, or 

 Euspira; and the largest known examples of either of these forms have 

 scarcely more than half the dimensions of the exami)le here described. 



DESCRIPTION OF TWO IVEW SPECIES OF SEBASTICHTIIVS (SEBA- 

 ST1C^3TE3VS EIVTOITIEI.AS AND SEBASTICHITIIYS RE10D0€EIL,0- 



RIS;, JFKO.TI ITIONTEBEY BA¥, CALIFORNIA. 



By I>AY1E> IS. JORDAN ami CHARLES H. GILBERT. 



Sebastichthys entomelas sp. nov. 

 Allied to *S'. oralis (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 thau the interorbital space, which is strongly con- 

 vex, especially in its middle part. 



]^asal spines minute. Preocular spine broad, triangular, rather prom- 

 inent, more conspicuous than in mclanops, but raucli less so than in 

 ovalis. Supraocular ridge little develof>ed, its spine minute, sliarp, con- 

 cealed by the scales. Postocular spine present, minute, similarly con- 

 cealed. Ko tympanic spine. Occipital ridges scarcely developed, 

 concealed by the scales, without distinct spine at tip. In ovalis all 

 these spines, though small, are distinct. Iwflavidus 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 



