620 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ut 



Amphidromus atricallosus (Gould, 1843) 



Plate 1 (figs. 1-3, 8-9) 



Bulimus atricallosus Gould, 1843, Proc. Boston Soc. Nat. Hist., vol. 1, p. 140 



[Philippine Islands (error)]. 

 Amphidromus atricallosus (Gould). — Laidlaw and Solem, 1961, Fieldiana, Zool., 



vol. 41, no. 4, pp. 530-531. 



This is a common and variable species in Peninsular and Southeast 

 Thailand. There are a few scattered records from the mountains 

 along the Cambodian border, but otherwise this species is unknown 

 from most of the country. Four distinctive color phases can be 

 recognized. They are: 



1. Typical atricallosus (pi. 1, fig. 1): parietal callus brown or 

 purplish-black with one or more dark varices on the spire. 



2. Form leucoxanthus von Martens, 1864 (pi. 1, fig. 8): one or 

 more varices present, but the parietal callus without dark markings. 



3. Form perakensis Fulton, 1901 (pi. 1, fig. 9): varices and 

 parietal coloration absent, subsutural white zone usually more marked 

 than in the other varieties. 



4. Form laidlawi, new color f orm ^ (pi. 1, fig. 3): whitish shell 

 with narrow, rather crowded, pale brown radial streaks that parallel 

 the lines of growth. One or more varices are usually present. 



The first three forms were described as full species, and their type 

 figures are markedly different in size, shape, and coloration. A. 

 atricallosus was based on the relatively large (50-55 mm. high), 

 elongated, bright yellow shells from Tenasserim, Burma; A. leucoxan- 

 thus von Tvlartens, on the whiter, more obese, slightly smaller shells 

 subsequently found in Southeast Thailand; and A. perakensis Fulton, 

 on the large, elongated, pale yellow shells with a sharply twisted 

 columella that are common in Perak and northern Malaya. The 

 variations in pattern, size, shape, and columellar configuration ex- 

 tend through the range of the species and it does not seem practical, 

 at this time, to delineate subspecific units. 



Color and columellar variation in the adult Thailand shells ex- 

 amined is indicated in the list of material by the following abbre- 

 viations : 



Li=leucoxanthus coloration 



'P=perakensis coloration with a distinct columellar plait 



S=laidlavn coloration 



2Holotype: USNM 363619 from Nong Khor, Southeast Thailand. Great 

 pleasure is taken in naming this beautiful new form after the late Mr. F. F, 

 Laidlaw of Foxearth, Sudburj^, Suffolk, England, who is responsible for my 

 interest in Amphidromus and who graciously allowed me the privilege of co- 

 authoring his catalog of the genus (Laidlaw and Solem, 1961), 



