32 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY- -IV. 
30.— ]TIICE1ST<I>D1IS Gill, ISG.'). 
('Gill, Proc. Ac. Nat. Sci. Pliila. 1865, 177: type Mici'into(hts punctatus Gill.) 
Tliiw is known from its teeth only. These are described as fol- 
lows: “The teeth are lixed and extremely minute, the largest little 
more than a line in length (in a shark “0 feet long) and decrease 
towards the ends of the jaw ; they are dis])osed in regularly transverse 
rows, of which then' are Kid to 1(17 on each side, while in front there 
an' Id to 1(1 in each transverse row; each tooth is recurved backwards 
and acutely ])ointed, swollen and with a heel-like projection in front 
rising from its base.” — (Gill.) {ritxpd-, small; if>z6r, an npright projection; 
fiddu', tooth.) 
40. yi. |>BlE5CtS5?MS Gill. 
A very large siiotted shark found in the (fnlf of California, ((fill, 
Proc. Ac. Xat. Sci. Phila. 18Go, 177.) 
Family XIV.— HETERODONTIDvE. 
{The Port Jachson I^IkoTh.) 
Sharks with two dorsal hns, both ]>rovided with spines; the lirst dor- 
sal oi)i)osite to the space between pectorals and ventrals; the second in 
advance of the anal. Body elongated, obtusely trihedral, gradually taper- 
ing from the anal region towards the caudal lin ; head high, with the fore- 
head declivous, little prominent; nostrils conlinent with the month; 
month rather narrovr, the upper lip divided into seven lobes, the lower 
with a fold ; spiracles small, below the lower })artof the eye ; no nictitat- 
ing membrane; gill-openings ratlier narrow; dentition similar in both 
jaws, viz, small obtnse teeth in front, which in the young are ])ointed, 
and i)rovided with three to live cusps; the lateral teeth large, i)ad-like, 
twice as broad as long, arranged in oblique series, one series being formed 
by much larger tc'cth than tho.se in the other series ; caudal lin moderate. 
Genera 1, 2, or 3 ; species about 4 ; inhabiting the Pacilic Ocean. Of much 
interest topaheontologists from their siqiposed relation to certain extinct 
tyi)es. {(kstriiciontula' (fiiiither, viii, 417, 41<S; but HeterodoniUH has 
])riority over Cestraeion.) 
* Branchial region longer lhan high, the .slits being little elongated ; nn'lar teeth flat 
and closely contignons GYUOPi,i:rKout:s, :U. 
3i.— «l:'ROFLEtIKOI>i:S Gill, ISGC. 
ptill, Proc. Ac. Nat. Sci. I’hila. ISSC, 489; type Ccjiracwn fr<nicisci Girard.) 
The eharacters distingnishing this grou]) from Heterodonfxs are thus 
given by Professor Gill: 
