394 Mr. VV. N. Lockington on the Porcellanidea 



of the tubercles and their interspaces iiniformly finely porous. 

 No oscula, and no distinct canal-sjsteni. 



Corpuscles small, consisting of a thickened centre from which 

 six to eight, smooth, straight, or slightly curved arms issue. 

 The union of these arms, either with the nodes or arms of 

 neighbouring corpuscles, produces a hexactinelliform lattice- 

 work (PI. VIII. fig. 5). 



The whole of the original specimen is set with spicules and 

 isolated siliceous corpuscles, only a portion of which probably 

 belongs to Mastosia. Geodia-\x\ie. spherules are the most 

 abundant. There are also large and small bacillar spicules, 

 pointed at one or both ends, small cylindrical spicules with 

 rounded ends, simple quadriradiates with smooth and spiny 

 arms, spicules with a short shaft and sliort forked anchors. 



This remarkable new genus is known only from the pas- 

 sage-beds of the White Jura e and ^ at Sozenhausen, near 

 Giinzburg, where it was obtained by M. Wetzler. The 

 largest specimens attain a diameter of nearly 2 decims. The 

 species is named Mastosia Wetzleri. 



[To be continued.] 



XLIV. — Bemarks ujyon the Porcellanidea of the West Coast 

 of North America. By W. N. LOCKINGTON. 



The accompanying list of Porcellanidea (which includes de- 

 scriptions of nine species I believe to be new, since they are 

 certainly distinct from any of those described or mentioned by 

 Stimpson as found upon this coast) does not profess to be 

 complete, but merely to give facts of distribution and other 

 particulars respecting forms with which I am acquainted. 



Stimpson, in his ' Prodr. des Anim. ^vert.' 1858, divides 

 the old genus Porcellana into the following genera : — Petro- 

 listhes, Pisosoma, Paj^hidopus, Pachycheles^ Megalohrachium^ 

 Porcellana^ Minyocerus, Porcellanella (White) , and Polyonyx. 



In the first two of these the first joint of the antennal base 

 is short, not reaching the margin of the carapax ; while in all 

 the others the first joint is more or less produced, and joined 

 to the margin of the carapax. 



The more convex carapax, stouter chelipeds, and less pro- 

 jecting front are the characters which separate Pisosoma from 

 Petrolisthes] but as some of my species have some of the cha- 

 racters of the former genus, while they are without others^ I 

 find it exceedingly difficult to discriminate. I have therefore 

 included Pisosoma in Petrolisthes, placing the former name in 

 brackets before the specific names of such species as, in my 



