In simmarizlng the observations made on rocky shores and 'bottoms, one cannot 

 avoid the impression that this pai'ticular h^titat alon{; the Pacific coast of Panama 

 presents most favoratile conditions for the flourishing of molluscan fauns. Both the 

 lamellihranchs and gastropods are re-oresented hy a large mim'ber of individuals helonging 

 to r}t\riy sriecies. The specimens are large and their shells heav:,". ^fhat particular con- 

 ditions are responslhle for the thriving of mollusks in these waters is not knovim, hut the 

 fact has heen noted already hy A. Agassiz (Zetek, 1913) who attributed it to the hydro- 

 graphical peculiarities of the Gulf of Panar.ia and adjacent v/aters. 



Sandy flats 



Only a fev: ohservations were made on sandy hottons, since pearl oysters are never 

 found in such hahitat. ITo diving v/as done on sand flats, and the material was collected by 

 hand kicking and dredging with a small rectanfiular dredge at a depth not exceeding ^5 

 fathor.is. The sand was usually of coarse variety, mixed v/ith broken shells and occasionally 

 with mTid. 



Several forms were found only in this particular environment. The most con- 

 s^oicuous of them is a very large sand dollar, Encope mlcropora L. Agassiz, about 13 cm. in 

 diameter. The characteristic feature of E. micropora is that the maximum height of its 

 body is anterior, between the abactinal system and the anterior edge (Clerk, 19^6), vAereas 

 in the closely related sTjecles, E. californica , it is posterior. Other species of sand 

 dollars previously reported from Pearl Islands (Clark, 19^b) , namely Encope perspectiva and 

 E. wetmorei , were not present in my collection. 



Another sea urchin which v/as freq.uently foxmd alive, and the shells of which are 

 often cast by the waves on sandy beaches, is Toxopneustes ro seus (A. Agassiz). Dr. Austin 

 Clark, who identified the specimens, remarks that the unusually large pedicellariae of this 

 s'oecies are •oov.'erf'ol stinging organs, so the sea urchin must be handled with caution. I 

 have not heard any complaints against the species from Panamanian fishermen, but according 

 to a Tiersonal communication from Clark, the related species, T. pileolus of the mid-Pacific, 

 is shunned by the natives, v/ho v/ill not touch it under any circumstances. It is reported 

 that occasionally it causes death among Japanese fishermen. 



A typical inhabitant of sand flats is a small gastropod, Cerithlum sp. , probably 

 C. macule suTi Kiener, about 30-35 ™^' lons- In certain places, as at Isla Santelmo 

 Tstation 15) this species was so abundant that a 10 minute drag yielded a dredge full of 

 live snails. 



Sand mixed v;ith mud provides the most desirable habitat for various clams, among 

 which the speci.es of Anadara and Area occupy prominent places. Live clams of these genera 

 v;ere freo_uently dredged or brought up by the divers, while dead shells were very abundant 

 on flats above low-v;ater mark. The largest of the clams was Anadara grandis Broderip and 

 Sovrerby. Specimens 12 cm. long, 13 cm. v^ide, and weighing over 3 pounds (both valves) are 

 rather common on beaches, especially in the vicinity of villages, for this clam is exten- 

 sively used for food. It is interesting to note that during pre-Columbian times, the 

 Indians cut dovm heavy shells of this clam to a sharp edge and employed them as scrapers. 

 Such crudely made tools found among various artifacts in the material excavated at the 

 Sitio ContI, in the province of Cocl^ were described and reproduced in the "Archaeological 

 Studies of Central Panama" (Lothrop, 1937» P- 95-96) conducted by the Peabody Museum of 

 Harvard University. 



Great numbers of A. grandis shells on beaches should not be regarded as an Index 

 of their relative abundance for the species is actively gathered by local residents, who 

 discard empty shells and scatter them around the dwellings. The same remarks apply to the 

 shells of the large snails, Malea rlngena and Galeodes patula , which species are extensively 

 used for food. 



Besides A. grandis , the clams are represented by Area pacifica Sowerby, which was 

 found virtually at every station, and by various species of Glycemeris , among v/hich 

 Gl^'cemeris raultlcostata (Sov/erby) predominates. 



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