KKTKCAYA. 
201 
<listinct. In Retecava carinata there is a thick, triangular keel on 
the obverse side, formed by the closely packed peristomes ; in 
R. pseudodisticlia, on the contrary, the peristomes are well spaced 
und often well raised, and separated by a median groove. This 
character is best developed in the variety is. The occurrence 
of fragments of both R. carinata and R. pBeudodhticlia at Magee 
Island is in favour of the identity of the two speeies. 
A third variety of this ‘ species ’ may be represented by the 
Eiyozoan described by Beissel as RJmonea irregularis, which has 
a double series of triserial apertures, separated by a well-marked 
anterior groove, and occurring on raised lateral crests. The upper 
part of Beissel’s figure agrees fairly closely with R. pseudodisticlia, 
but the lower part is thicker and irregular. Beissel suggested that 
the form might be only a variet}' of R. pseudodisticlia. 
LIST OF SBECBIENS. 
British. 
B. 446. Three fragments (ou slide) . Middle Chalk. Chatham. Gamble Coll. 
B. 970. Two fragments (on slide). IMiddle Chalk. Chatham. Vine Coll., 
Xo. 26. Becorded by Tine as Idmonea carantina. 
B. 972. Three fragments with especially distant peristomial series. Middle 
Chalk. Chatham. Vine Coll., No. 22. 
B. 3272. Five fragments (two? det.). Chalk. Between Black Head and 
Gobbins, Magee Island, X. Ireland. Presented by Jos. Wright, Esq. 
B. 971. A slender branch (ou slide). Middle Chalk. Chatham. Vine Coll., 
Xo. 27. 
B. 456. Three fragments. Middle Chalk. Chatham. Gamble Coll. 
B. 4501, B. 4502. Two branches (on slides). Middle Chalk. Chatham. 
Gamble Coll. 
B. 530. Fragment of var. pliformis (ou slide). Middle Cbalk. Chatham. 
Gamble Coll. 
B. 3980. Four fragments of var. fiHformis (ou slide). Middle Chalk. 
Chatham. Gamble Coll. 
B. 4500. One fragment of var. Jiliformls (on slide). Upper Chalk. Bromley. 
Simmons Coll. 
Foreign. 
B. 3547. A fragment of a thicker zoarium (on slide). Maastrichter Kreide. 
IMaastricht. Van Breda Coll. 
B. 3779. A worn fragment in the condition of I. lineata, Hag. Maastrichter 
Kreide. Geulem. Gamble Coll. 
B. 3233. A zoarium of var. maculata. Maastrichter Kreide. Maastricht. 
Van Breda Coll. 
