46 



MAZATLAJT BIVALVES 



same colour, lunular purple ray on one valve only.— 145, 9 sp. 

 same colour, purple rays absent.— 146, 10 sp. and 2 valves, 

 pale yellow: this is the most frequent state.— 147, 8 sp. 

 white, normal shape.- 148, 8 sp. white, transverse.— 149, 12 

 sp. white and pale yellow, with irregular pale violet concen- 

 tric bands.— 150, 5 sp. orange yellow, s imil arly banded.— 

 151, 5 sp. stained with purple and green. — 152, 15 sp. yellow, 

 green at umbos and posterior slope.— 153, 15 sp. whitish, band- 

 ed with violet, green at posterior slope.— 154, 9 sp. plain yellow 

 with greenish slope.— 155, 9 sp. white with greenish slope.— 

 156, 7 sp. orange yellow stained with purple.— 157, 2 sp. and 

 Ijalve, do, highly coloured, form approaching D. Conradi.— 

 158, 6 sp. with broad bro-rni rays.— 159, 6 sp. with verj- faint 

 rays. — 160, 5 sp. shewing distorted growth. 



Besides these were foimd a few scores of specimens which, 

 when examining D. punctatostriatus I have generally turned 

 over to D. Conradi ; when examining the latter, have been dis- 

 posed to turn back again. They are here grouped according to 

 the preponderance of characters.— Tablet 161 contains D. pimc- 

 tatostriatus approaching D. Conradi, 4 sp. whitish.— 162, 6 sp. 

 yellow.— 163, 3 sp. i-ayed.- 164, 2 sp. yellow, transverse.— 165, 

 3 sp. reddish, transverse.- 166, 3 sp. whitish, nan-ow margin. — 

 167, 3 sp. very gibbous.— In all 192 shells, the result of very 

 frequent elimination from an examination of many thousand 

 specimens ; no two probably being exactly alike. 



75 (b.) DONAX ? PUNCTATOSTRIATUS, Vat: C^LATUS. 



D. ? punctatostriatus, t. maxime incBquilaterali, margine ven- 

 trali vix anguJato .- superjleie posticd dense lii'atd, Ihvs ex- 

 pressis radiaiitihiis : intet'stitiis dense decussatis, lineolis ralde 

 tinprcssis : sculpturd partem versus anteriorem, in lineas punc- 

 iarum mutante, punctis angulatis : 7nargine plerumque simplici, 

 epidermide detisd rugosd tectu. 



iS^eai'ly 40 specimens have occurred, agreeing in the above 

 characters, while only 2 shewed the least disposition to depart 

 towards the ordinary type. Shape extremely injvquilateral, 

 Jintorior end much prolonged. Sculptiu-e deeply marked on 

 the ])osterior and posterior ventral part ; with elevated ridges, 

 and the furrows not simple rows of dots as in D- punctato-stria- 

 tus, but witli short lines impressed as with a file-cutter's tool. 

 These gradually subside anteriorly into punctate striation. but 

 even then the dots are angidated, not round. There is a large 



