I 
266 MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
are sparsely scattered, irregularly disposed, longer translucent spicules; 
surface of the valves minutely uniformly reticulate under the lens, appear¬ 
ing smooth to the unaided eye; the mesial suture evident, the fifth valve 
widest, the posterior valve very small with a subcentral inconspicuous 
vertex at the anterior third; anterior valve with nine, middle valves with 
two, posterior valves with two slits, the interior lines of which are marked 
by a row of minute pores; the middle of the valves on each side of the 
median suture conspicuously porous internally. Length in alcohol, 8; max¬ 
imum breadth, 6 mm. (Dali.) 
Type in United States National Museum, No. 383018. Type locality, 
St. Paul Island, Bering Sea. 
Range. Bering Sea. 
Schizoplax brandtii Middendorff, 1846 
Bulletin , Imperial Academy of Sciences, St. Petersburg, 6: 117. Tryon and Pilsbry, 
Manual of Conchology, 14:47; PI. 11, figs. 32-37. 
Chiton minutus testa externa ovata, nitidula fusco olivacea lituris un- 
dulatis longitudinalibus et maculis laete aeruginosis circumscriptis elegan- 
tissime notata. Valvae laeviusculae, sub lente incrementi strias distinctas, 
et superficem minutissime ac aequaliter granulosam exhibent; areis laterali- 
bus carina tumida vix distinctis.In summa linea mediana val- 
varum intermediarum, superne sulcus decurrit linearis longitudinalis, cui 
inferne opponitur canalis profunde et abrupte incisus, commissura antica 
valvarum singularium interrupts.Incisura lateralis Valvarum inter¬ 
mediarum supra nondum, infra vix conspicua.Valva antica den- 
tibus marginalibus 14.Valva ultima margine postico convexo 
dentibus 13.Pallium marginale viride glabrum setis microscopicis 
fimbriatum. Branchiarum series ab initio secundae tertiae ad finem tertiae 
quartae partis totius corporis longitudinis porrigitur. Lamellularum Bran- 
chialium numerus circiter 22.Adulti longitudo 0.16 decim. (Mid- 
dendorff.) 
Shell oval, rather elevated, the jugum rounded; olive-brown, streaked, 
maculated or clouded with blue, sometimes chestnut. Umbo central, irregu¬ 
larly planate. Lateral areas scarcely defined. Entire surface smooth, seen 
under a lens to be finely granulated in quincunx. Girdle narrow, olive- 
ashen, maculated, closely beset with minute spines, but appearing almost 
smooth to the naked eye. The median valves have a sharply cut longi¬ 
tudinal median sulcus. The jugal sinus is moderate, deep, scarcely lami¬ 
nate, conspicuously spongy. Eaves small, very spongy. Anterior valve 
with 11, posterior 11, and median valves with one slit. Length, 16; width, 
5 mm. (Tryon and Pilsbry, Manual of Conchology.) 
[ 868 1 
