1865.] OF MOLLUSKS FROM MAZATLAN. 271 
rounded ribs, which are evanescent near the umbo. Inside with a 
very few strong teeth, developed in a curved line. 
698. ScissURELLA RIMULOIDES, 0. sp. 
S. ¢. rapide augente, albida, tenuissima ; apice celato; anfr. 
il., radiatim liratis, liris subdistantibus, acutis, obliquis ; um- 
bilico magno; labro declivi, haud Jisso, sed apertura postica, 
ut in“ Rimula” formata, subquadrata, elongata; liris trans- 
versis gradus teste increscentis definientibus ; peritremate con- 
tinuo, obliquo. 
Only one specimen was found of this beautiful little Species, the 
first known from America. It looks like a Velutina crossed by 
sharp ribs in the direction of the slanting mouth. In the first whorl 
the ribs are very close. It then assumes its normal sculpture, but 
there is nearly a whorl before there is any trace of incision. This 
appears to have begun as a slit, which was afterwards closed up. A 
band, marked off by ten transverse ribs showing stages of growth, 
encircles the shell as far as the hole, which is long and somewhat 
rectangular; but there is no band between the hole and the outer 
lip. The shell furnishes a complete transition to Rimula. It is 
preserved on tablet 2532. 
Long. *023, long. spir. 003, lat.-03; div. 140°. 
Hab. Mazatlan ; off Spondylus calcifer ; Liverpool Collection. 
699. VITRINELLA ORNATA, 0. sp. 
V. t. subdiscoidea, diaphana, tenuissima ; anfr. iv., quorum iii. 
primi nucleosi, insculpti; ultimo carina maxima circa periphe- 
riam ; postice subangulata, rugis radiantibus et striolis spt- 
ralibus ornata; antice carinata, carina nodosa; basi carina 
altera et rugis radiantibus ornata; umbilico angulato, satis 
. magno; labro a carina indentato. 
Long. ‘015, lat. -028--035 ; div. (cire.) 175°. 
Hab. Mazatlan; one specimen off Spondylus, on tablet 2533; 
Liverpool Collection. 
700. ViTRINELLA TENUISCULPTA, 0. sp. 
V. t. planata, diaphana, tenuissima ; anf. il. et dimidio, quorum 
iil. nucleosi; striis elevatis, spiralibus, quarum una magna, 
quasi carina prope suturam sculpta; peripheria haud angu- 
lata ; bast bis angulata, interdum rugis radiantibus distantibus 
ornata ; umbilico satis magno, carinato ; apertura undata, sub- 
quadrata. 
The sculpture is not uniform over the last whorl. The principal 
diagnostic features are the biangulated base, the infrasutural keel, 
and the rounded periphery. 
Long. 016, long. spir. 0, lat. -023--03 ; div. 180°. 
Hab. Mazatlan; one specimen off Spondylus, on tablet 2534; 
Liverpool Collection. 
