P II L A S. 



Species 21. (Mus. Boston). j 



Pholas semicostata. Pho. tcsld parvd, hrevi, ventri- 

 cosd, cute testacea antice clauso, postice in tubam 

 prolongato ; testd in media oblique divisd, antice 

 subacute sinuatd, distanter costatd, postice leviter 

 rugata, hrevi. 



The half-kibbed Pholas. Sliell small, short, vuntri- 

 cose, closed anteriorly and elongated jHisteriorly 

 by a testaceous integument into a tulie ; shell 

 obliquely divided in the middle, anteriorly rather 

 acutely sinuated, distantly ribbed, posteriorly 

 lightly wrinkled, short. 



Lea. Pro. Bost. Soc. Nat. Hist., Nov. 18M, pi. x.\iv. 

 f. 1. 



Hah. South Carolina. 



The regular part of the shell, which has almost the 

 form of a Teredina, is supplemented and extended by 

 less laminated structure, filling up the liiatus in front 

 and forming a tapering tube towards the ])Osterior 

 extremity. 



Species 22. (Mus. Brit.) 



Pholas p.ivicola. Pho. testd clausa, cimeiformis, trans- 

 verse canali divisa ; parte anticd oblique dimi- 

 diatd, versiis dorsum striatd, versus marginem 

 ventralem Icevigatd, ventricosd; parte posticd 

 elongatd, laminis Jimbriatis cutaneis angulariter 

 disposiiis ornatd ; valvulis dorsalibus duabus, sub- 

 quadratis. 



The kiver Pholas. Shell closed, cuneiform, trans- 

 versely divided by a canal ; the anterior part 

 obliquely divided in half, striated towards the back, 

 smooth, ventricose towards the ventral margin ; 

 posterior part elongated, ornamented with fringed 

 cutaneous layers angularly disposed. Dorsal valves 

 two, subquadrate. 



SowEKBT. Proc. Zool. Soc, is K.i. 



Hab. Gunny Taboor, River Pantai. 



This species was first collected by Mr. Arthur Adams 

 in a part of the river in Borneo twelve miles distant 

 from the sea, where the water was perfectly fresh. 

 Tlie singular fringed lamina" of epidermis distinguish 

 this freshwater species from all others. 



Species 2;!. (Fig. a, b, Mus. Brit.) 

 Puolas melanuka. P/to. testd clausd, subovati, in 

 medio canali serrato divisd ; parte anticd imbri- 

 catim costatd, margine ventrali Imviyato, inflato 

 dorsa coiiJlncHte, margine dorsali valide rejiexo et 

 tiunidu, ad ambones scutis duabus subquadratis 

 super lamiuas latas dispositis diviso ; parte 

 2iostico concentrice lyratd, epiderniide nigricante, 

 ad terminum tumuUs cornels, inflatis, subrenifo7-mis 

 duabus ad tubam testaceam affixis. 

 The black-tailed Pholas. Shell closed, subovute, 

 divided in the middle by a serrated canal ; anterior 

 part with imbricated ribs, ventral margin smooth 

 inflated, confluent with the back, dorsal margin 

 strongly reflected and tumid, divided at the 

 umboes by two subquadrate shields placed upon 

 wide laminre ; posterior part concentrically ridged, 

 with a blackish epidermis, and at the end two 

 homy, inflated, subreniform swellings fixed to tlie 

 shelly tube. 



SowEiiBV, Proc. Zool. Soc, 18o4. 



Ilah. Monte Christo. 



A fine characteristic species found by the late Mr. 



Cuming in hard clay and loose stones. 



Species 24. CFig. a, b, Mus. Cuming in Brit.) 

 Pholas BUAXCULvrA. Pho. testd pyriformi, clausd, 

 antice ventricosd, in partes tres oblique divisd ; parte 

 anticd prope marginem ventralem IcBvigatd, medio 

 et ad dorsum minute scabroso-striald ; parte medid 



August, 1872. 



