46 'MAZATLAN BIVALVES 



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

 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, similarly 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 

 1 valve, do, highly coloured, form approaching D. Conradi. 

 158, 6 sp. with broad brown rays. 159, 6 sp, with very faint 

 rays. 160, 5 sp. shewing distorted growth. 



Besides these were found a few scores of specimens which, 

 when examining D. punetatostriatus 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. pune- 

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

 yellow. 163, 3 sp. rayed. 164, 2 sp. yellow, transverse. 165, 

 3 sp. reddish, transverse. 166, 3 sp. whitish, narrow 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 ? PUNCTATOSTHIATUS, var. CJELATUS. 



-D. ? punetatostriatus , t. maxime incequilaterali, margine ven- 

 trali mx angulato : superjicie posticd dense liratd, liris ex- 

 pressis radiantibus : interstitiis dense decussatis, lineolis valde 

 impresses : sculpturd partem versus anteriorem, in lineas pwic- 

 tarum mutante, punctis angulatis : margine plerumgue simplici, 

 epidermide densd rugosd tecto. * 



Nearly 40 specimens have occurred, agreeing in the above 

 characters, while only 2 shewed the least disposition to depart 

 towards the ordinary type. Shape extremely inequilateral, 

 anterior end much prolonged. Sculpture deeply marked on 

 the posterior and posterior ventral part ; with elevated ridges, 

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

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

 These gradually subside anteriorly into punctate striation, but 

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



