14 PROCEEDINGS OF THE CALIFORNIA 



gin ; ambulacral star non-symmetrical ; petals unequal, open at their extremi- 

 ties. Anterior petal straight, longer than the others ; the lateral ones nearly 

 straight, diverging from the apex with an angle of about eighty degrees ; pos- 

 terior petals very short, sub-oval, having the anterior side most curved. Four 

 rows of pores in each petal ; the inner pores transverse, the outer ones pointed 

 obliquely inwards. Mouth posteriorly sub-central ; anal-aperture small, sub- 

 marginal. Ambulacral furrows double, nearly symmetrical, slightly ramified. 

 Each ambulacral and iuter-ambulacral space is occupied by two rows of irreg- 

 ular plates, either pentagonal or hexagonal. Tubercles numerous, crowded in 

 the ambulacral furrows, but much worn off in the specimens examined. 



Locality : Kern Lake, Buena Vista County. 



The specimens described are in the collection of the Academy ; they were 

 found by Dr. Gibbs, to whom the species is dedicated. 



Obs. — This species, considered by Mr. Gabb as of probably miocene age, is 

 closely allied to the S. striatula, which is found living on the Californian coast, 

 and occurs fossil in the faluns (miocene formation) of Bordeaux, France ; but 

 it differs from it in the outlines and the size of the shell, the former being com- 

 paratively small and longer than broad, while the latter is broader than long. 

 Besides, the apex of the S. Gibbsii is situated more posteriorly, and the lateral 

 petals, in the S. striatula, diverge from the apex, with an angle of from one 

 hundred and ten to one hundred and fifteen degrees ; this latter has also its 

 ambulacral furrows more ramified at their extremities. 



S. interlineata W. P. Blake. 



Disk sub-circular, broad, upper surface convex towards the middle, depressed 

 on the margins, plane beneath ; apex central ; ambulacral star symmetrical : 

 petals long, equal, closed at their extremities, nearly reaching from the apex to 

 the margin of the shell, terminated by five or six irregular hexagonal plates. 

 The petals are longitudinally divided into four rows, which are connected by 

 numerous and regular transverse lines of pores. Mouth central ; anus sub- 

 marginal ; ambulacral furrows symmetrical, not much ramified. Inter-ambu- 

 lacral areas occupied by two rows of pentagonal plates, convex, of equal length, 

 increasing in size until they unite with the ambulacral plates ; hexagonal from 

 that point and decreasing towards the margin. 



Two sorts of appendages ; spinous processes numerous and crowded, above 

 and beneath. Spines of the superior surface short, striated, pyriform, irregu- 

 larly pentagonal or hexagonal ; inferior spines slender, comparatively long, 

 dentaliform, striated longitudinally, tubular and round. 



Obs, — Water-worn fragments of this fine fossil occur in abundance on the 

 beach, between Merced Lake and the Pacific, south of Point Lobos, in San 

 Francisco County. It was made known to science by Mr. W. P. Blake. Geol- 

 ogist of the Railroad Survey, who found it in 1853, among the shingles 

 thrown up by the surf, and first described by Mr. W. Stimpson. At that time 

 the locality whence the scutella? were derived had not been discovered, so that 

 the specimens obtained being imperfect, no complete description could be made ; 



