TECHNICAL NOTES AND BIBLIOGRAPHY 249 



for some hours, and subsequently kept in live cars for 

 indefinite periods. In such freshly caught animals, the 

 urine sodium concentration may considerably exceed 

 that of the plasma. 



The rectal gland of the elasmobranchs should not be 

 confused with what this writer {59} some years ago 

 called 'Marshall's gland,' which is appendicial to the 

 genitourinary system (rather than the intestine), and 

 which has been described only in some (perhaps not 

 all) Batoidei (skates). The secretion of Marshall's gland 

 has a high concentration of sodiimi bicarbonate which 

 apparently protects the sperm from the acid urine (the 

 bladder in the female empties into the top of the uterus) . 

 The highest recorded bicarbonate concentration for Raja 

 stabuloforis is 115 millimols per liter {59}, but Dr. 

 Thomas H. Maren, working at Salisbury Cove in 1959, 

 has found in R. oceUata a concentration of 322 millimols 

 per hter (pH 10)— by a considerable margin, the highest 

 value known in any secretion. 



Kempton {64} has challenged the older statement 

 that the elasmobranch tubule contains a unique segment. 

 In the spiny dogfish, Squalus acanthias, he finds only the 

 typical 'proximal' and 'distal' portions, but it is not cer- 

 tain that these are truly homologous with the correspond- 

 ing segments in the Amphibia and mammals. 



The term 'ovoviviparous' means producing eggs that 

 have a well-developed shell as in oviparous animals, but 

 which hatch within the body of the parent, as in the case 

 of many elasmobranchs and reptiles. The exceptions to 

 ovoviviparity among the elasmobranchs are the orders 

 Chimaeroidei and Cestraciontes (and in the order Eu- 

 selachii, the families Scylliorhinidae and HemiscyUidae) ; 

 in the order Tectospondyli, the family Somniosidae; and, 

 in the order Batoidei, the family Raiidae. The order Ces- 

 traciontes includes among its living representatives the 

 rare primitive sharks, Chlamydosehchus and Heterodon- 

 tus. All the Euselachii are viviparous except the Scyl- 



