No. 11, سب‎ On some Young Stages in the Development of Hippa, 
Porcellana, and Pinnixa. By WALTER Faxon. 
I. Hippa talpoida. 
Durna the month of August, 1877, I procured large numbers of Hippa 
talpoida on the bathing-beach near Nobska Point, Wood's Hole, Massachusetts, 
the locality made known by Professor S. I. Smith. Among them were many 
ovigerous females, from which I obtained the first stage of the larva, Asa 
supplement to Professor Smith’s paper on the early stages of this animal,* I 
present the following description and figures of the first zoóa-stage, Smith's 
series beginning with what he presumes to be the second zoéa-stage. 
The carapace (Plate I. Figs. 5, 6, 15) is oval, smooth, strongly convex above, 
curving downward and inward on the sides. It sends a long blunt process 
forward below the eye-stalks (Plate I. Fig. 6 b) Behind, it presents a deep 
sinus for the accommodation of the abdomen (Plate I. Fig. 15 6), Anteriorly 
it is produced between the eye-stalks into a short, broad, rather blunt rostrum. 
The carapace has no dorsal or lateral spines. At the points where the lateral 
spines appear after subsequent moults, there is a thickening of the integu- 
ment, producing a very slight bulge on the outer surface, a stronger one within 
(Plate I. Fig. 15 a). 
The abdomen has nearly the same form as in the later stages of the ۰ 
It consists of but five segments, counting the telson. The first abdominal seg- 
mént of the adult is fused with the second or with the thorax, the sixth with 
the telson, The fourth segment in the abdomen of the larva is considerably 
wider behind than in front. The telson is quite different from the telson as 
seen in Smith’s figures of the later stages. Its breadth now slightly exceeds 
its length, and the curve of the sides is such that nearly the maximum width 
is reached but a short distance from the anterior border. From the middle it 
narrows slightly posteriorly, to be produced at the posterior angles into a stout 
tooth. As in the later stages, the convex posterior margin of the telson is fur- 
nished with spines and minute teeth (Plate I. Figs. 13, 14). The number of 
spines is the same as in the later stages, namely, twenty-six, the eighth, counting 
from either side, being the longest ; but the number of denticles between the 
spines is much less than in the later stages. Starting with the single median 
denticle, the spines are separated by single denticles until the tenth spine is 
* The Early Stages of Hippa talpoida, with a note on the Structure of the Mandi- 
bles and Maxille in Hippa and Remipes. By Sidney I. Smith. Trans, Conn. Acad. 
111, pp. 811 ۰-942 Pl. XLV. - XLVIII, ۰ 
