290 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Table II. 



This table enumerates in brief the characters of the sinus of the girdle 

 and its armature, and the chief distinctive i^eculiarities of each group. 



Siuus. 



Simple, smooth, deep 

 Simple, broad 



Simple, broad, shallow. 



Broad, spongy 



Obsolete 



Broad, shallow 



do 



Extremely small 



Most minute . . . 

 Broad, shallow. . . 

 Broad, fissured . . 



Moderate 



Broad or minute . 

 Broad, smooth... 



Simple, broad, deep. 



.do 

 .do 



Simple, narrow, deep . . 

 Simple, broad, shallow. 



do 



do 



? Broad, shallow, some- 

 i times dentate. 



Broad, shallow, laminate. 



Narrow, deep, laminate. . 

 Narrow, shallow, simple . . . 



Rounded, simple 



Narrow, shallow, simple. 



Broad, shallow, simple. 

 Squared, denticulate... 



Girdle. 



G-ravelly scales, smoo th or striated 

 Spicules and chafly scales 



"With hairs or fine spines 



Solid, downy, poriferous 



Thin, hoiny, tiiiely granulous . 



Granular tlattish scales 



do 



Long, horny scales 



Smooth, downy 



Smooth or downy 



Smooth 



Thin, smooth 



Hairy 



Short, striated, shelly bristles 



Spongy, downy 



Irregular, chafify scales 



do 



Long, striated spines and scales.. 

 Double series scales, not chafly . . 



Small, transverse scales. 

 do 



Large, smooth, imbricated scales. 

 Narrow, with small scales 



-do 

 .do 

 .do 



Small, laminae united. 



(?) 



Large, laminaj united 



Large, waved, laminaj 

 united. 



)Large, waved, lobed, lam-( 

 i inoB united. ( 



Minute, waved, smooth 



Simple, lamina} separated. . 



Smooth, with marginal tufts 



Minute bristles and sutural hair- 

 tufts. 

 Pleshy with long, hairy bristles. 

 Smooth, with homy processes 



Spongy, with scattered soft hairs. 

 Large, solid, imbricate scales 



do 



Smooth or downy . 

 Smooth, spreading 



Hairy 



' ' Minutissime asperulus " . 

 Large, solid, grooved scales . 



Shelly bristles 



.do 

 .do 



Narrow, smooth, laminate. 

 Narrow, laminae separated . 



Narrow 



Nan-ow, lobed . 



Narrow, very deep . 

 Deep, lobed.' 



do 



Shelly spines 



Shelly bristles, spreading . . 



Smooth, small, downy tufts. 

 Granular bristles 



Bristly, striated scales 



Broad", with shelly bristles. 



Thin, lanugate 



Thin, lanugate, wide, with sutural 



pores. 

 Slit behind, solid smooth scales. . 

 Produced in front, upright scales . 



Slit behind, minute spiculse 



Large, separate scales, bristles 

 between. 



Peculiarities. 



All negative. 



Flattened mucro, valves thrown 

 forward 



Laminai only on anterior valve. 



Terminal valves laminated. 



IJuslit laminai on all valves. 



Short gills, granular scales. 



Radsioid central slits. 



Small sinus, reticulate girdle, 

 crowded propped teeth. 



Smooth girdle. 



Short gills, ischnoid plates. 



Valves slit in dorsal axis. 



Teeth few, valves partly immersed. 



Ischnoid plated, hairy i,irdle. 



Radsioid slits i.schnoid plates, stri. 

 ated bristles. 



Half immersed valves, plates isch- 

 noid. 



Body long, chaffy scales. 



Same as last, with radsioid slits. 



Same, triple series of striated scales. 



Body normal, double series of 

 scales. 



Body normal, small striate scales. 



Body normal, radsioid slits. 



C Scales of Chiton, plates of JscTiwo- 



< chiton. 



( Same, with radsioid slits. 



Narrow girdle, highly sculptured, 

 plates curved outward. 



Curved plates, marginal pores. 



Propjjed teeth, sutural pores. 



Tough, fleshy girdle, propped teeth. 



Propped teeth, horny girdle pro- 

 cesses. 



Spongy girdle, single lateral slits. 



Broad' seiTated teeth and sinus, 

 scaly girdle. 



Same, wit li added side slits. 



Sharper teeth, sin-joth girdh;. 



Sharper teeth, vahc^ parily cov- 

 ered. 



Non Assured but deeply pectinate 

 teeth, hair,\ girdle. 



Posterior valve ' ' medio fimbriata." 



Non-imbricat(- scales, broad groov- 

 ed and seviate teeth. 



Teeth short inside, long outside, 

 waved sinus. 



Same, with radsioid slits. 



Spinous girdle, lobed sinus. 



Partly covered valves, radsioid 

 slits. 



Downv girdle tufts, smooth sharp 

 teeth. 



Bristly girdle, smooth propped 

 teeth. 



Sliarp teeth, striate scales. 



Long, sharp teeth, radsioid slits, 

 posterior mucro. 



Twisted niiicni, smooth, thin girdle, 

 thin isi-hiKiid valves. 



Smooth, porous gin.le partly cover- 

 ing valves, veiy long teeth. 



Slit tail-plate, scaly girdle. 



Sharp teeth, prv)duccd girdle, bi- 

 lobed scales, lobed siuus. 



Very long and narrow, deep slit. 



Scaly girdle, flattened tail-plate. 



