GLOSSARY. 



845 



to the ligament when it consists of a 

 split cylinder in the form of a 

 C-spring, as in Venus. 



Pascagula beds — middle Miocenic of 

 Mississippi. 



Paspotansa — subdivision of Pamunkey 

 formation, Eocenic of Atlantic coast. 



Patelliform — shaped like Patella; a de- 

 pressed hollow cone. 



Patulous — expanded ; slightly spread- 

 ing. 



Pawnee limestone — middle Carbonic of 

 Kansas. 



Pectinate — comb-like. 



Pectinated rhombs — paired pore clus- 

 ters in the calyx of certain cystoids 

 (see Fig. 1775). 



Pedicle — a stalk. In brachiopods, the 

 fleshy stalk by which the animal is 

 anchored (see I., 171). 

 Pedicle opening — in brachiopods, the 

 opening at the beak of the pedicle 

 valve for the passage of the an- 

 choring pedicle. 

 Pedicle valve — in brachiopods, the 

 ventral and usually the larger 

 valve : through it the pedicle is ex- 

 tended posteriorly. 



Peduncle — a stalk ; a pedicle. 



Pelagic — referring to the open sea. 

 Those animals are pelagic which live 

 in the open sea and are thus inde- 

 pendent of the bottom. 



Pen — in modern squids, the horny in- 

 ternal skeleton ; the proostracum. 



Pendent — hanging suspended, 



Pennington shale — upper Mississippic 

 of southern Appalachians. 



Penta — a prefix, meaning five. 



Pentagonal — having five angles. 



Pentameroid — similar to Pentamerus 

 (see I., 178, 3). 



Pentamerons — in five parts. 



Penultimate — next to the last. 



Pereiopoda — in Crustacea, the locomo- 

 tor appendages proper (see Fig. 

 1692). 



Perforate — with an opening; in echi- 

 noids, used in reference to the ambu- 

 lacral areas; also to the presence of 

 a pit in end of a mamelon. 



Peri — a prefix, meaning around or be- 

 yond. 



Periderm — the transparent, external, 

 chitinous covering of Hydrozoa which 

 expands into the cups or hydrothecse. 



Perignathic girdle — the girdle of cal- 

 careous pieces surrounding the peri- 

 stome on the inside of an echino- 

 derm test. 



Periostracum — the epidermis or outer 

 organic covering of shells. 



Peripheral — relating to the circumfer- 

 ence, the outside portion or surface. 



Periphery — the circumference ; the 

 boundary line of any closed figure. 



Periproct — in echinoids, a small, mem- 

 brane-covered aperture on the upper 

 side of the test. The anus opens near 

 the center of this area (see Fig. 191 1, 

 B, pt.). 



Peristome — the edge of an aperture ; 

 the membrane surrounding the mouth 

 of an invertebrate animal. In bryo- 

 zoa, the elevated rim of a cup or 

 zoecium (see Fig. 201, c). In echi- 

 noids, a large, membrane-covered 

 aperture on the under side of the 

 test. The mouth opens in the center 

 of this (see Fig. 191 1, C, pt.). 



Peritheca — the more or less wrinkled 

 calcareous envelope surrounding the 

 basal portions of a compound coral- 

 lum. It corresponds to the epitheca 

 of a corallite. 



Petal — in echinoids, a petaloid ambu- 

 lacrum. 



Petaloid — resembling in outline a leaf 

 or petal. In echinoids, applied to 

 those ambulacra in which the two 

 pore-bearing zones of each ambula- 

 crum separate between the apex and 

 the circumference of the test and 

 contract again (petal-like) more or 

 less perfectly before reaching the cir- 

 cumference (see Figs. 191 1, P; 1923. 

 a; 1934, ^)- 



Phosphatic — containing phosphorus. 

 Phragmocone — the chambered middle 

 shell in some Dibranchiate cephalo- 

 pods (see II., 24; also Figs. 1512, 

 1513, b). 



