as 



It may wctt be that migration took place both along the north 

 Eurasian coast and across the sea bordering the continent of 

 North America. The striking similarity of many of the local 

 races of Tbais lapillus found in the Atlantic to related forms 

 occurring upon our Pacific Coast, seems more than a mere 

 coincidence. On the other hand, all of the lapillusAWit ioxTM 

 of our west coast intergrade completely when examined with 

 a large enough series, while the range of variation is not greater 

 than that of the Atlantic forms. The tendency of taxonomists 

 has been togradually reduce the number of recognized species 

 through the relegation of many of the older trivial names to 

 the synonymy, leaving us with the three forms listed by Dall 

 in 1915, with a number of varieties, including lima Martyn 

 1784, canaliculata Duclos 1832, and ^mf^r-^zn^/a Dcshayes 1839. 

 Since thee^ thr:e forms intergrade completely, there seems to 

 be no valid reason for regarding them as specifically distinct, 

 any more than would hold for the distinctive local races of 

 lapillus of the Atlantic or lamellosa in the Pacific. The taxo- 

 nomic problem in dealing with such material, and the matter 

 of suitable labeling, is one that is common to all cases of highly 

 polytypic species. If the three above mentioned species were 

 consolidated it would leave us with a single wide spread and 

 highly polytypic species - Thais lima Martyn- comparable in 

 diversity with its Atlantic relative. As to whether lima in its 

 turn should be consolidated with lapillus^ as has been suggest- 

 ed by several competent authorities, remains an open question. 



As will be seen from the above discussion, our knowledge of 

 the ecology and genetics of the Thais forms is based almost 

 cx<:lusivcly upon critical observational, physiological and gen- 

 etic studies of the Atlantic species. We still await however, 

 the experimental cross-breeding of selected forms to determine 

 the manner in which the various hereditary factors arc related. 



Since up to this time no experimental observations dealing 

 with Tbais lamtllosa are on record, the conclusions of the wri- 

 ter, based as they are upon purely observational data, may be 

 regarded as somewhat tentative. 



