74 /. W. Jackson — -The Brachiopod Liothyrella. 



With regard to the mesial dorsal septum, though this appears to 

 be occasionally" absent in the genotype of Liothyrina, viz. L. vitrea, 

 it is present in tvro of my specimens from the Mediterranean as 

 a slight, but distinct, ridge between the muscle scars. One shell is 

 of large size with a thick test, but otherwise agrees with normal 

 L. vitrea. Fine radial strise are present on all my specimens. The 

 radial striae of L. vitrea was noted by Fischer and Oehlert in 1891/ 

 as well as the thickening of the test and the presence of a mesial 

 septum in thick shells. L. vitrea thus possesses the three essential 

 characters upon which the new genus Liothyrella is founded. 



Liothyrina ciihensis (Pourt.), another northern species, often 

 regarded as merely a form of Liothyrina sphenoidea (Phil.), supplies 

 us with contributory evidence. lu one of my specimens from the 

 coast of Mexico, which agrees exactly with Davidson's'' and 

 Blochraann's^ figures, the radial striae are present, but are very 

 indistinct; there is also a slight thread-like ridge between the 

 muscle scars in the dorsal valve. In two specimens of the same 

 species from Porto Rico (100 fathoms) the radial strias and slight 

 mesial septum are also present, the latter showing through the shell. 



In 1908 Blochmaiin (op. cit., pp. 612-25) divided the genus 

 Liothyrina in two groups according to the presence or absence of 

 certain calcareous spicules at the base of the cirri (Cirrensockeln). 

 The first group, that in which the spicules are present, is widely 

 distributed, and includes L. affinis, Calc. (Mediterranean, Azores, 

 etc., and possibly West Indies), L. arctica, Friele (Iceland and 

 Greenland), L. antarctica, Blochmann (Antarctica), L. winteri, 

 Blochmann (St. Paul, Indian Ocean), L. uva, Brod. (Magellanic 

 region and Western American coast to Mexico). With these he 

 provisionally included L. davidsoni, Adams, L. elarlceana, Dall, 

 L. fulva, Blochmann, and L. moseleyi, Davidson. The second group, 

 without the basal spicules, comprises L. vitrea (Born), L. sphenoidea, 

 Philippi, L. cubensis, Pourt., L. bartletti, Dall, and L. sfearnsi, 

 Dall & Pilsbry. This group occurs chiefly in the Mediterranean 

 Sea and Atlantic Ocean, but one species (Z. stearnsi) is found off the 

 east coast of Japan. Another species (Z. cernica, Crosse), found at 

 Mauritius, is also referred to this group, though neither spiculae nor 

 brachidium are known. The figures of Z. bartletti and Z. stearnsi 

 given by Blochmann (op. cit., pi. xxxix, figs. 27, 29) distinctly show 

 that each possesses a dorsal mesial septum. 



Since Blochmann made this division other forms have been 

 described, viz. Z. uva, var. notorcadensis, Jackson (South Orkneys, 

 South Georgia, and Western Antarctic), and Z. blochmanni, Jackson 

 (Antarctica).* The former appears to belong to the first group, the 

 latter to the second group. Further examples of Z. fulva, from 



^ Exped. Sclent, du ' ' Travailleur et du Talisman, 1880-3": Brachiopodes, 

 Paris, 1891, pp. 51, 57. 



^ " A Monograph of Eecent Brachiopoda," pt. i : Trans. Linn. Soc, ser. il, 

 ZooL, vol. iv, pt. i, pi. ii, figs. 19-196, 1886. 



•^ ' ' Zur Systematik und geographischen Verbreitung der Brachiopoden ' ' : 

 Zeit. fiir wissen. ZooL, Bd. xe, pi. xxxviii, figs. 2l-21c, 1908. 



* Jackson, op. cit., pp. 375, 378. 



