126 THE NAUTILUS. 



nearly flat, with a broad, slialJow posterior sinus, the scarcely 

 raised mucro being at the posterior third. 



The interior is nearly white, strongly striate across the cen- 

 tral part, wliere some valves may show a green or pink stain. 

 The posterior valve has a rather deep posterior sinus and a 

 single slit on each side. 



The girdle is rather narrow in dry si)ecimens, and bears 

 coarse processes covered with sharp white spines. 



Length 23, width 12.2 mm. 



San Pedro, California, collected by Mr. Herbert N. Lowe. 

 Type no. 117951 A. N. S. P., paraiype in Lowe coll., no. 1538. 



This species is related to M. sinuata, M. imporcaia and M. 

 porifera, but it apparently differs from all of them by the 

 profusely spiny girdle processes, which are not exclusively 

 localized at the sutures, though often present there, as well 

 as scattered over the girdle elsewhere. The allied forms men- 

 tioned are all from northern localities. 



In some of the specimens there are 10 to 12 ribs on the 

 anterior valve. The younger shells are suffused with lilac 

 inside. 



MOPALIA IMPORCATA LIONOTUS n. subsp. 



This chiton agrees closely with M. imporcaia except that 

 there is a narrow, smooth jugal tract. The lateral areas are 

 granose between the coarsely tubercular diagonal and sutural 

 ribs. The anterior valve has 10 ribs. Posterior valve is de- 

 pressed behind the mucro, which is at the posterior fourth. 

 Interior light Niagara-gi'een, darker posteriorly on each valve. 

 The girdle bears branching processes, often like the branches 

 of spines on a cactus. These are scattered, sometimes sutural. 



Length 15.5, width 9 mm. Divergence 95°. 



White Point, collected by Mr. H. N. Lowe. Also San 

 Pedro, same collector. Type no. 117952 A. N. S. P. ; para- 

 type no. 1542 Lowe coll. 



Mop ALIA MUSCOSA LAEViOR u. subsp. 



This name has long been used in the collection for the form 



