Fan shells I Piriiig. lanceolate . Sov;erliy, v.'hich freq.uently produce lilack pearls are 

 aTmndant at ir.any stations; some of the largest specimens were more tlian 30 cm. long. 



UaD^r hea\n/- shelled clans v;ere found on liottoiii betvreen the rocks. Anong then, the 

 most comnon are the orange-colored Macrocalista aurantiaca (So'./er-oy), various species of 

 Tivela, and Antigona rigida Dillwyn. Hone of these clams is used by the local population 

 for food. 



Edible oysters, Ostrea iridescens &ray (Tig. 20) and Ostrea columblensis Hanley 

 v/ere found attached to rocks a fev: inches belov; lov;-water mark. They have very thick 

 shells, purplish inside; and are grov.dng in groups, preferably in the vicinity of small 

 creeks v;hich empty Into the sea. The meat is palatable, but was too salty, and lacked 

 flavor. There was but little deposition of glycogen, and the gonads were ripe. The shells 

 of 0. iridescens were heavily infested by Lithophagae. 



Among the large gastropods, the most abundant v/as the already mentioned conch, 

 rasciolaria princeps . Empty shells of this snail v;ere frecuently occupied by hermit crab, 

 Aniculus elegans Stimpson. ITert in a.bundance v;ere Galeodes patula , Strombus peruvianus, 

 7asum caestus , Strombus gracilior G-ra;.', Malea ringens , Cyratium tigrinum -, and various 

 species of Murex (M. nigritus , regius, princeps ) , which are freouently found in large 

 numbers over a relatively snail area of bottom. Many empty shells of M. nigritus were 

 found along the mainland coast in the Gulf of Chiriq.ui (Station 26). Occasionally, odd- 

 looking live specimens of Fusinus dupetitthouarsi (Ziener) were picked up among the rocks. 



numerous Porcellanid crabs v;ere seen in this habitat. My collection includes the 

 following species, identified by 7. A. Chace, Jr.: Petrolisthes armatus (Gibber), 

 Petrolisthes edv;ardsii (Saussure) , and Petrolisthes sp. Besides the already-mentioned 

 hermit crab, Aniculus elegans Stimpson, the collection contains Petrochirus calif orniensis 

 Bouvier, Eriphia sq.uamata Stimpson, Trapezia cymodoce ferruginea Latreille, and Ocypode 

 gaudichaudii H. Milne Bd^ifards and Lucas. 



rigure 20 Ostrea iridescens at low-water level in tidal zone around 



Pearl Islands. Used for food. Notice infestation of shell 

 by Lithophaga (left). 



31 



