Dr. F. M tiller on the Transformations of the Porcellanse. 47 



the L. neglecta of Alder, and is as graceful in form as it is fairy- 

 like in size. The markedly flexuose character of the stem, the 

 great length and narrowness of the cells, the plain margin, and 

 the Lilliputian size, are the distinctive points. 



IX. — On the Transformations of the Porcellanae. 

 By Dr. Fritz Muller, of Desterro*. 



[Plate I.] 



For two years I have been acquainted with a Zo'e'a which is 

 distinguished from its allies by the want of the dorsal spine and 

 the unusual length of the straightly extended frontal horn; but 

 it is only a few months since I found it to be the offspring of 

 the same Porcellana whose extraordinary parasites I described 

 in my recent memoirs f. In the mean time I met with oppor- 

 tunities of examining the young brood of two other Porcellanida. 

 One of these is a smaller Porcellana with a nearly circular 

 carapace, which occurs rarely on rocks amongst Polypes and 

 Polyzoa; the other (PI. I. figs. 1-3) lives parasitically upon some 

 species of Starfishes, and differs so much from the true Por- 

 cellana in its whole appearance, in its claws, and especially in 

 the shortness of the external antennas, that I regard it as the 

 representative of a peculiar genus, and call it Porcellina stelli- 

 cola J. 



As these Porcellana-hvvsd agree in all essential characters with 

 the Zoea-fovm* of the young Crabs, I leave their detailed de- 

 scription for a larger work on the young state of the Crabs, for 

 which I have long been collecting materials, and confine myself 

 at present to a superficial description of their structure. 



The carapace is of an oval form, and covers not only the upper 

 part and sides of the anterior unsegmented part of the body, 

 but also the first five segments of the abdomen. From its 

 anterior margin issues a straight spine or horn, which is as 

 much as five times the length of the carapace (three times in the 

 smaller Porcellana). Two similar spines extend straight back- 

 wards from the hinder margin of the carapace ; these are usually 

 parallel, but sometimes divergent in Porcellina ; in the smaller 

 Porcellana (fig. 10), in which they attain only two-thirds the 

 length of the carapace, they are slightly bent downwards at the 

 apex, and bear, near their origin, a considerable spine directed 



* Translated by "W. S. Dallas, F.L.S., from Wiegmann's Archiv, 1862, 

 p. 194. 



t See Annals, July and August 1862. 



% Another Porcellana (P. Creplinii, n. sp.) is still more singular in its 

 mode of life ; it resides in pairs in the tube of Chcstopterus pergamentaceus. 



