THE PHILIPPINE LAND MOLLUSKS OF THE GENUS 



OPISTHOPORUS 



B}^ Paul Bartsch 



Curator, Division of Mollusks and Cenozoic Invertebrates, United stuff* 



National Museum 



In the Cyclophoridae, as in the Annulariidae, we find in some 

 groups wonderful provision for breathing - , even when the mollusk 

 has tightly closed its shell with its operculum. One of these de- 

 vices is characteristic of the genus treated in this paper — Opistho- 

 porus. This genus is closely allied to the widely distributed and 

 profusely specifically differentiated genus Eucyclotus, which it re- 

 sembles in general form, in color pattern, and in the structure of the 

 operculum. It is. however, at once distinguished from Eucyclotus 

 by the presence of a breathing tube, a slender curved hollow horn 

 open at its tip and at the shell end, which furnishes a breathing pore 

 when the mollusk withdraws into its shell and closes its door with 

 its operculum against undesirable visitors or enemies. 



The type of the genus, Opisthoporus bioiliatus Mousson, was de- 

 scribed from the Botanic Garden at Buitenzorg. Java, whither it 

 was transported with plants from Borneo. The genus seems cen- 

 tralized in Borneo. It extends north into the Philippines as indi- 

 cated in the present paper and south into Celebes, Singapore. 

 Sumatra, and Java. 



The character of the breathing tube is shown in the illustrations 

 of the various Philippine races on Plate Si and the operculum 

 in Figure 1. The relief map (pi. 82) figures the distribution of 

 Opisthoporus in the Philippine Islands. 



OPISTHOPORUS QUADRASI PALAWANENSIS, new subspecies 



Plate si. Figure ."> 



issi). Opisthoporus quadrasi Dohkn, Nachrichtsbl. Deutschen Malak. <Jes.. p. 

 .">. in parr. 



1897. Opisthoporus quadrasi Kobelt and Mollendokff, Nachrichtsbl. Deutschen 



Ma Ink. Ges., vol. 29, p. 119, in part. 



1898. Opisthoporus quadrasi Mollendorff, Abh. Naturf. Ges. Gorlitz, vol. 22, 



p. 185, in part. 



Shell large, thin, semitranslucent, very depressed helicoid. The 

 first two whorls pale chocolate-brown, the rest vellowish horn 



107726—32 323 



