MUSEUM OF COMPARATIVE ZOOLOGY. 261 
ber. Several individuals moulted once or twice, but beyond a slight increase 
in size, a growing opacity of the shell, and the change in the telson noticed 
above, little alteration was discernible. 
On looking at the proportions of the adult Porcellana macrocheles (Fig. 11 و‎ 
the carapace of this specimen measured 9mm. in length by 12.5 mm. in 
width) one might be inclined to doubt its identity with our young form ; but I 
have material at hand to show that the widening of the carapace is the gradual 
result of growth, In a specimen 3.5 mm. broad, caught, free-swimming, at 
Newport on the 30th August, 1865, by Mr, Alexander Agassiz,* of which he 
made a sketch at the time, the breadth of the carapace exceeds its length by 
one fifth, In a specimen from Charleston, S. C., 6 mm. broad, the carapace 
is less than one fourth broader than long. 
As the delicate integument of the young becomes indurated by the deposi- 
tion of calcareous salts, and the aération of the blood devolves more and more 
exclusively upon the gills, the carapace broadens with the expansion of the 
respiratory chamber. This change in the proportions of the carapace is com- 
monly seen in the Brachyura when a graduated series from very small to adult 
specimens is examined, and Carcinologists cannot be warned too often against 
establishing new species upon juvenile characters. 
List of Works relating to the Development of Porcellana. 
Hartstonn and Wrstwoop, Descriptions of somo Species of ‘Crustaceous Animals. 
By S. HArnsTONE, JUN., Esq. With Illustrations and Remarks, by J. O. Wrst- 
woop, Esq., F. L. S., ete. Loudon's Magazine of Natural History, Vol. VIII. 
pp. 261-277; Figs. 28, 29, May, 1835. 
This paper contains descriptions and figures of a series of young specimens of Por- 
cellaswe from Hastings, England (P. minuta Westw.; probably the young of P. lon- 
gicornis, M. Edw.). The smallest of these specimens measured 2 mm. in length, and 
was used by Westwood as an argument against the probability of a metamorphosis in 
Porcellana, which had recently been announced by J. V. Thompson. 
THOMPSON, J. V. Memoir on the Metamorphosis in Porcellana and Portunus, En- 
tomological Magazine, Vol. IIT. pp. 275-277, Fig. 1, Oct. 1835. 
This is the first published notice of the zoéa of Porcellana.+ Thompson actually 
* Mr. Agassiz has another drawing of a young Porcellana raised from the zoéa at 
Newport, August 17, 1875, which seems to indicate the occurrence of a second species 
on the coast of New England. In this form the front is prominent and triangular, 
the dactyli of the ambulatory feet long and without the accessory claws of Polyonyv. 
The length of the carapace is 8 mm., its breadth slightly less. 
+ According to Claus, who ignores the observations of Thompson, Couch, and 
Dujardin (Marburger Sitzungsberiehte, 1867, p. 12; Untersuchungen über Crus- 
taceen, p. 57), the larva of Porcellana was described under the name of Zonchophorus 
anceps as early as 1825 by Eschscholtz. (Bericht über die zoologisehe Ausbeute 
während der Reise von Kronstadt bis St. Peter- und Paul. Isis von Oken. 1825, 1, 
col. 734 ; Taf. V. Fig. 1.) The animal here referred to, as is evident from the fig- 
ure, is the Brachyuran zo&a afterwards described by Dohrn (Zeits, Wiss. Zool. XXI. 
