MAZATLAK BIVALVES 47 



smooth lunular portion, not specially coloui*ed. The margin 

 is generally simple, nearly as in D. Conradi : and when it has 

 the intercalary grooves proper to D. punctatostriatus, they are 

 rarely carried up into intercalary rows of dots. The epider- 

 mis is remarkably thick round the margin. Colour sometiuies 

 white, occasionally yellow, but generally stained with rich 

 reddish purple. Whether it be an aberrant variety of D. punc- 

 tatostriatus, or a distinct species, must be determiaed when 

 more specimens have been examined, or the animals studied. 

 The largest but not characteristic specimen measured long. "91, 

 lat. 1-37, alt. -57. 



Sab. — Mazatlan ; very rare ; L'pool Col. 

 Tablet 168 contains 3 specimens, white, yellow and purple. 



76. DoNAX CoNEADi, DesL 



Proc. Zool. Sac. 1854, p. Sol.—Rve. Conch. Icon. pi. 5, sp. 29. 



+ D. contusus, Rve. Conch. Icon. pi. 4, sp. 24. 



+ D. CaKfornicus, Conr. teste Besh. ms. B. M. & Col. Cuming : 



nequaquam, teste Nuttall. 

 + D. culter, Sanl. Proc. Zool. (Soe. 1845, p. 14. — Rve. Conch. 



Icon. pi. 4. sp. 21. 



It is not without the most careful, laborious and often 

 repeated examination of upwards of 1,000 specimens that I have 

 felt compelled to depart from the views of the illustrious 

 Deshayes and the very accurate Hanley, and grouj) together 

 the species above quoted. The D. Californicus, teste Nuttall 

 whose shells were the basis of Conrad's descriptions, is very 

 different from the shells so named by Desh. in the Br. Mus, 

 and Col. Cuming ; the former being a smooth, gibbous, sub- 

 triangular shell, more like a young D. punctatostriatus, though 

 quite distinct. The name Conradi is preferred to culter which 

 has priority, as expressing the adult form, and as leaving 

 contusus and culter for the use of those who believe in the 

 species, -^^ithout introducing confusion. The shells wrongly 

 called D. Californicus are simply the white variety of the forms 

 contusus and culter. 



This creature loves liberty both in form and colour. The 

 shape is generally transverse, not unlike the large variety of 

 D. anatinus, slightly swollen ventrallj', with a flattening towards 

 the posterior end. Sometimes it tapers off at the anterior part, 

 which is then somewhat flattened : sometimes the whole shell 



